Mr. Kessler reaches back seven years to 2005 for the case of NTP v. Research-In-Motion, the famous case against the Blackberry manufacturer, for his justification and concern about NPEs, but in recent years it is the major players in high tech have been suing each other over patents. The companies in the news for patent sales, patent purchases, and patent lawsuits are not NPEs but the high tech goliaths including Google, Apple, Microsoft, Motorola, Oracle, Facebook, AOL, and Yahoo among others. Purchasing patent portfolios can be used defensively against other companies and just as easily these patent purchases can be used, and are being used, as offensive weapons against competitors. Patent trolls are simply the bogeymen used by large companies to convince politicians to “reform” patent laws.

Mr. Kessler argues that the extension of the patent term to 20 years, enacted in 1995 to make U.S. patent law consistent with the World Trade Organization’s Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPs), is a problem because “in technology things move a lot faster.” I do not understand the reasoning behind this complaint. If technology moves so fast, then a patent becomes worthless long before the term is over. What does it matter if a patent is valid for five years or 50 years if the patent is worthless after five years?

Mr. Kessler states the “we have to stop allowing juries to establish the value of patents… the market… [should] determine value. ” In fact, the market does determine value. The majority of patent lawsuits are settled before reaching court, and both parties determine a fair value based on free market principles. A negotiation between two parties is a great example of such free market principles where each party determines the value of the patent with respect to its own interests, free from other considerations. For cases that reach a jury, the jurists are provided information by economists and accountants who determine the value of a patent based on the market value of the products that embody the patented inventions. Of course we can argue about whether their models and calculations are correct, but our entire justice system is based on juries determining values and awarding damages and so if Mr. Kessler believes that juries are incapable of determining value, then he is implying that our entire legal system-at least the civil system-is flawed. If that is true, then it is the legal system as a whole that needs to be revised.

Perhaps the most disturbing recommendation is to require patent holders to manufacture or sell products. This requirement would fundamentally damage the patent system. Patents allow small, cash-strapped inventors to create something new and protect that invention from large corporations that have the money and resources to kill it or steal it before the inventor can get funding or market share. I know this from experience. Years ago I created a software tool
that I sold to a large company that enabled that company to sell their expensive hardware to customers in the communications industry. Each software package, that sold for about $25,000, enabled this company to sell their multimillion dollar equipment to communications companies that otherwise would never have been customers. The arrangement seemed good to me, but the large company made it clear that they did not like being beholden to me, so after several years of buying my software, they created their own. My sales immediately went to zero-in other words I became a non-practicing entity. Fortunately I had patented my invention and so I had more leverage than the large company expected. Had Mr. Kessler’s recommendation been in effect, I would have had no recourse against that large company.

According to Kessler, James Madison was the man behind Article 1, Section 8, Clause 8 of the U.S. Constitution, giving Congress the power “to promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.” Historical documents suggest that Thomas Jefferson and Charles Pinckney also lobbied for this clause. In any case, this section of the Constitution has been the justification for our patent system for over 200 years. Mr. Kessler believes that Mr. Madison did not understand what he was doing or, at best, did not foresee the expense that patent litigation would involve in the 21st century. In fact, the founding fathers knew exactly what they were doing when writing the intellectual property clause into the U.S. Constitution. They were protecting the individual from the overwhelming power of large entities. They were enacting the very principles of American society for which we fought the Revolutionary War. Since 1790 the U.S. patent system has contributed to America becoming the most innovative society in the history of the world. Fundamentally changing the system in the ways suggested by Mr. Kessler would stifle that innovation.

The most significant change is to BitMatch. When examining binary object code to find text strings, you can now specify the encoding format of the file. If you’re not sure about the encoding, you can choose multiple formats.

As demand for our products increase outside the United States, we realized a need to support languages in those countries also.

1. Abstract. This is a one-paragraph description of the invention that’s being patented.
2. Drawings. These are carefully labeled figures that are used to illustrate important concepts of the invention and that are described in the detailed description. It is important that at least one diagram shows a block diagram of the invention if the patent includes apparatus claims. For a physical device, a diagram should show the physical parts and their relationships. For software, the diagram should show the architecture of the software. For a patent that includes method claims, at least one diagram should have a flow chart that illustrates the method.
3. Background of the invention. This section describes the field of the invention, other inventions, or publications that predate this invention (“prior art”), and other inventions related to this invention. This section typically explains the inventions usefulness—what’s so great about the invention and why people will want it.
4. Summary of the invention. This is typically one paragraph to one page in length that describes the invention. Though this section isn’t legally required by law, it’s a part of almost every patent.
5. Brief description of the drawings. For each drawing in the patent, there should be one or two sentences to briefly describe it.
6. Detailed description. This section explains the invention as completely as possible, referencing the drawings. This section describes what is called the “embodiment” of the invention that differentiates it from existing inventions. The description must explain the best way the inventor knows of implementing the invention, and it must be detailed enough to allow “one of ordinary skill in the art” to produce it. Remember that the patent must be novel, nonobvious, and useful.
7. Claims. This is the essence of the invention. Each claim is a single sentence, though it’s usually a very long sentence broken into multiple parts, that describes the invention in as precise wording as possible.

There is often debate among patent attorneys, inventors, and patent litigators about the definition of “one of ordinary skill in the art.” The Manual of Patent Examining Procedure (MPEP) section 2141.03 defines one this way:

The person of ordinary skill in the art is a hypothetical person who is presumed to have known the relevant art at the time of the invention. Factors that may be considered in determining the level of ordinary skill in the art may include:

(1) type of problems encountered in the art;

(2) prior art solutions to those problems;

(3) rapidity with which innovations are made;

(4) sophistication of the technology; and

(5) educational level of active workers in the field. In a given case, every factor may not be present, and one or more factors may predominate.

Note that the definition of one of ordinary skill in the art will vary depending on many factors and cannot be defined generally, but must be defined for each particular patent.

Claims are the most important part of any patent. Patents typically contain anywhere from 5 to 30 claims. Each claim is a single sentence, and each describes an important aspect of the invention. Whether another product infringes on a patent ultimately comes down to these claims.

One last piece of advice: never file a patent that you’ve written yourself without having a qualified patent attorney or patent agent review the claims. I’ve seen patents for ingenious devices that were worthless because of one misplaced word in a patent claim. Other patents had no value because the claims were so narrow that no one infringed, or avoiding infringement required some insignificant change to the invention.

1. Copyright infringement; or
2. Infringement or violation of any of the protections contained in the DMCA (Digital Millennium Copyright Act) including its anti-circumvention provisions; or
3. The sale or promotion of counterfeit goods.

The shutdown of the website is effected by disabling DNS translation. When a user types in a URL such as www.ZeidmanConsulting.com, the network devices that implement the Domain Name System (DNS) throughout the Internet, called “DNS servers,” translate the characters into an Internet Protocol (IP) address consisting of numbers such as 205.134.253.65.

Recently the web domain registrar GoDaddy announced that it supported the bills. Shortly thereafter, angry Internet users at blog site reddit called for a boycott of GoDaddy and, not surprisingly, GoDaddy competitors immediately jumped in by offering users discounts to jump ship. To date, over 40 Internet companies have come out against the bills (see here)*. The House issued a paper listing over 140 companies that have come out in favor of the bills (see here). GoDaddy gave in to the pressure and reversed its position on the bills.

Renowned attorney Mark Lemley and colleagues David S. Levine and David G. Post wrote a recent article for the Stanford Law Review entitled Don’t Break the Internet. You can tell from the title where they stand, but I’d like to address each of their main points.

The Bills Will Not Harm Internet Infrastructure

These authors claim that “the bills represent an unprecedented, legally sanctioned assault on the Internet’s critical technical infrastructure.” The authors go on to say that implementing such filtering “threatens the fundamental principle of interconnectivity” and “will also have potentially catastrophic consequences.” I’ll give them the benefit of the doubt that they’re not trying to simply use exaggerated scare tactics, but rather they just don’t understand the technical issues.

Every time you register a new domain, the DNS servers throughout the Internet are updated with the translation. This is part of the normal course of events. Every time a domain name expires, the DNS servers are again updated to remove the translation. According to a report by VeriSign, there were 4.9 million new domain name registrations in the third quarter of 2011. That’s about 37 DNS changes per minute on average, not counting changes due to expired domains. From a technical point of view, the bills do nothing different than what happens many times each day on the Internet and has no technical challenges or risks whatsoever.

The Bills Do Not Violate Basic Principles of Due Process

These authors go on to state that these acts “violate basic principles of due process… by depriving persons of property without a fair hearing and a reasonable opportunity to be heard.” I’ll assume that these attorneys have never watched the TV show Law and Order, or any other cop show, or taken part in a criminal investigation where a court orders a warrant, based on evidence, that otherwise violates a person’s constitutional rights because there is evidence of illegal activity. These bills, as with all similar bills, require a court to make a decision to take action or not. I’ll assume that the authors of the paper have also not spent much time in a courtroom, because as an expert witness I can tell you that no judge takes such a decision lightly and that there are high thresholds of proof. Without this kind of ability to shut down illegal activity, accused criminals would simply avoid showing up for court in order to evade punishment.

The Bills Do Not Violate Free Speech Rights

These authors claims that each bill is an “unconstitutional abridgement of the freedom of speech protected by the First Amendment.” I’ll assume that the law professors are a little rusty on constitutional law particularly with respect to the First Amendment. Many types of speech are not protected such as hate speech, child pornography, and speech that infringes on copyrights.

The authors go on to claim that “[t]he Constitution requires a court ‘to make a final determination’ that the material in question is unlawful ‘after an adversary hearing before the material is completely removed from circulation.’” In other words, you cannot take down a website until you allow the accused to appear in court to defend himself. This quote is taken from the decision in the case of Center for Democracy & Technology v. Pappert. Again I’ll give the authors the benefit of the doubt that they were just too busy to actually read the court’s decision, but you can do so by clicking on the link. The full decision reads a “publication may not be taken out of circulation completely until there has been a determination  of obscenity after an adversary hearing” (emphasis added).This case is about the conflict between free speech rights and an accusation of child pornography, not about free speech rights and copyrights. But a case about free speech and copyrights on the web already has a precedent. Years ago the Digital Millennium Copyright Act (DMCA) was similarly challenged in federal court and survived. The decision in U.S. v. Elcomsoft confirmed that restrictions in the DMCA were not a violation of due process and did not conflict with the First Amendment.

In fact, copyrights have been enforced in this country as long as the constitution has been around, and longer than the Bill of Rights because their protection is given in Article I, section 8:Congress shall have power… To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.

The formal codification of copyright law took the form of the Copyright Act of 1790, before the adoption of the Bill of Rights in 1791. So the First Amendment’s protection of speech and the Copyright Act’s provisions for injunctive relief, seizure, and forfeiture coexisted easily for over 200 years without conflict. Terry Hart explains the history of the relationship between copyright and free speech in his extensive article here and in several other well-researched articles on his Copyhype blog.

The Bills Would Not Turn the U.S. Into a Repressive Regime

The authors’ final point is made with this statement:

It would be not just ironic, but tragic, were the United States to join the ranks of… repressive and restrictive regimes, erecting our own “virtual walls” to prevent people from accessing portions of the world’s networks.

Repressive regimes are actually those that do not protect individual property rights, but rather allow the government to determine who owns what, or conversely allows property theft to go unpunished. Repressive regimes do not allow individuals to protect their own property but require the government to do so on their behalf. Repressive regimes do not have the court system and the legal system of the United States that strict procedures and requirements to be met. Repressive regimes do not have the checks and balances in their government systems to allow one organization, corporation, government branch, or individual to challenge any law and any action taken by any other organization, corporation, government branch, or individual. Repressive regimes concentrate power in a few elite, not in individuals. There is no realistic concern that this law will turn the U.S. into a repressive regime.

Copyright and Trademark Infringement on the Internet is a Very
Real Problem

In their conclusion I find surprising agreement with the authors. They state:

Copyright and trademark infringement on the Internet is a very real problem, and reasonable proposals to augment the ample array of enforcement powers already at the disposal of IP rights holders and law enforcement officials may serve the public interest. But the power to break the Internet shouldn’t be among them.

They are absolutely correct. We must find reasonable ways to stop infringement of intellectual property on the Internet. Such a solution must be fair to the victim of the infringement. It must uphold the principles of the Constitution of the United States. And it must not break the Internet. SOPA and PIPA may not be perfect implementations of such protection, but they meet all of these requirements. There may be better strategies that can be reached through measured and thoughtful debate, but not through excessive hyperbole and fear.

*It doesn’t surprise my to see Scribd on this list. I play a regular game of whack-a-mole trying to remove illegal, free copies of my articles and books on this site that just pop up again within a few weeks after I send them a DMCA takedown notice.

There are some other heartening things in the report. In the foreword to the report, WIPO Director General Francis Gurry makes four critical points:

1. Firms are investing historically unprecedented amounts in the creation of intangible assets – new ideas, technologies, designs, brands, organizational know-how and business models.
2. Innovation-driven growth is no longer the prerogative of high-income countries alone; the technological gap between richer and poorer countries is narrowing. Incremental and more local forms of innovation contribute to economic and social development, on a par with world-class technological inventions.
3. The act of inventing new products or processes is increasingly international in nature and seen as more collaborative and open.
4. Knowledge markets are central within this more fluid innovation process. Policymakers increasingly seek to ensure that knowledge is transferred from science to firms, thereby reinforcing the impact of public research. Moreover, ideas are being co-developed, exchanged and traded via new platforms and intermediaries.

This large growth has resulted in new, emerging markets dealing with IP such as brokerages for purchasing, selling, trading, and auctioning IP, consulting companies for managing IP, valuing IP, and supporting IP litigation, and software for analyzing, valuing, and comparing IP.

One of the key, and most controversial changes, is a shift in the patent priority rules from the “first-to-invent” system that has been in effect in the US since the beginning of patent law to the “first-to-file” system that is used in every other patent system in the world. A first-to-invent system means that the first person to invent something gets the patent. This seems fair. A first-to-file system grants a patent to the first person, or company, to pay the fees and file the patent. This, to me, seems un-American in that it rewards paperwork over innovation.

To those who believe there is no such thing as American exceptionalism—those who believe that there is no more innovation in the US than anywhere else—this change “harmonizes” our patent system with the rest of the world, making patent law fairly consistent from country to country.

If you’ve read my blog you know that I believe that there is more innovation in the United States than anywhere else on earth. Do we really need proof of this? But let’s take another look at this issue. Proponents claim that this change will have an insignificant effect, if any. Yet has anyone rigorously studied how this change will affect individual inventors and entrepreneurs in America? Until recently, the answer was no. But professors of law at the University of Pennsylvania, David S. Abrams and R . Polk Wagner, recently performed a detailed study.

You might wonder how they could perform such a study when the act does not require the “first-to-file” system to go into effect until March 2013? These professors already had a model. Canada switched from first-to-invent to first-to-file in 1985, giving them a significant amount of historical data. The results are interesting, and unfortunately not hopeful.

The chart below illustrates one of many interesting statistics in their study. The number of patents per year before the system changed was fairly constant at around 1,700 per month. A significant drop of over 40% occurred around the time that the system changed, to less than 1,000 per month and remained low.

Perhaps even more disconcerting is that Abrams and Wagner find that the fraction of patents going to individual inventors also decreased at the time of this change in Canadian patent law. So the number of patents decreased and the percentage of patents issued to individual inventors also decreased.

Abrams and Wagner summarize their findings in very blunt terms:

In the end, how much do individual inventors matter? That,
we think, is the critical question suggested by our study. To
date, most observers seem to have assumed that a shift to the
first-to-file rule, though a substantial change in US patent
law practice, would have little impact on who seeks and receives
patents. This is wrong. A change to the first-to-file rule in
the US should be expected to result in the reduction of individual
inventors’ share of patents. Thus, the cost savings yielded
by the change away from first-to-invent will not, we suggest,
be free.

Like any law, this patent reform act can be undone. However, it seems that many members of both parties support this change, probably because they do not fully understand the implications and because of pressure from large corporations that stand to gain from it. Perhaps a grass roots movement can rise up to pressure Congress to un-reform US patent law. Grass roots movements seem to be all the rage these days. So I still hold out some hope.

• The Software IP Detective’s Handbook
• About Software Copyrights
• About Software Trade Secrets
• About Software Patents
• The Software Clean Room Process

I’ve been thinking about that, and I’ve come to three conclusions.  First, many programmers just aren’t very good at what they do. Many  of them have simply learned to copy others’ code (see  Is Googling Replacing Programming?) or maintain someone else’s code. Second, many programmers underestimate their abilities. Programmers tend to be introverted and not ones to brag about their skills. Of course there are exceptions, but programming is generally a solitary endeavor.

Third, many programmers believe that to be patentable, something must be very complicated. But that’s not true. Section 102 of the U.S. Patent Act states that an invention must be novel, and Section 103 states that it must be nonobvious. There is no requirement that it be complex.

Many inventions are very useful and yet also very simple. Searching Google, I found almost 4,000 patents involving paper clips. I found 27,000 patents with the word “needle“ in the title and over 9,000 patents for kinds of spoons. There are nearly 600 patents involving rubber bands. Some recent patents include a water sprinkler for dogs (USPTO # 7,997,229) and a waterproof cover for a camera (USPTO # 7,991,274). My point is that some inventions are simple and some are complex, but they all are novel and no one else thought of them. If you tend to dismiss software patents, remember that what makes an invention patentable is not whether you could have done that, but whether you actually did.

Grocery trolls produce no fruits, vegetables, or produce of any kind. They do not own farm land, they do not raise livestock. They do not harvest grains. Instead, they buy up the food items produced by small, independent farmers, and sometime large farm corporations, and force hungry consumers to buy them at higher prices. These greedy grocery trolls, going by benign names like Safeway, Lucky’s, Rainbow Grocery Cooperative, and Trader Joe’s have no farming skills whatsoever. And the consequences of not buying food from them? Starvation!

Patent licensors perform the same kind of service by buying up inventions from inventors and offering them for sale. The strength of their size, their sales force, their marketing budget, and their distribution channels ensures that they will be able to buy from small entities and sell to large and small entities and make a profit by charging for their services. Groceries buy from small farmers who could not otherwise reach large markets. Patent licensors buy from small inventors who cannot afford to license their inventions to other companies.

The analogy isn’t perfect, but it’s pretty darned good. Free commerce in a free society means that you or I can sell anything we like to anyone we please; there are no restrictions on having created the good in the first place. If that were the case, most transactions would be illegal. You wouldn’t be able to sell your house or buy a used car. You wouldn’t be able to trade baseball cards or collect antiques. The list is very long. That’s why restrictions on the sale of patents must never be allowed in any free market economy. Restricting the sale of any goods would be a curtailing of civil rights-an extremely dangerous precedent-and anyone who believes in civil liberties should be absolutely against such restrictions.

Leonardo da Vinci is considered the quintessential "Renaissance Man," one who excels at all forms of intellectual endeavors. He is honored as a genius, some say the greatest genius the world has ever known-an artist, a mathematician, a scientist, and an engineer. But does he deserve these accolades? No. And bestowing them upon him belittles those who truly are great mathematicians, scientists, or engineers.

Leonardo da Vinci definitely created great artwork, though for my taste he doesn’t match the grandeur, detail, or power of Michelangelo his peer. Da Vinci invented painting techniques like sfumato for creating a delicate shading for more realistic human features, though other techniques for which he is credited were actually developed by other painters such as and chiaroscuro that was developed and perfected by Caravaggio, Correggio, and Rembrandt¹. I acknowledge he was a great artist-he created artwork that has been appreciated worldwide for centuries. But da Vinci, known for a problematic lack of attention, rarely finished any of his works. The Last Supper painting is incomplete². His Gran Cavallo horse statue was never finished³. He left the monastery of San Donato before finishing the Adoration of the Magi that he had been commissioned to produce⁴. The list goes on. Even the Mona Lisa background seems to me drab and amateurish, like an attempt to just get the portrait done so he could move on, a fact described by a witness to the original painting, Giorgio Vasari, a biographer and painter himself⁵. Modern day art historians and fans of da Vinci make all kinds of excuses for his impatience and impulsiveness. One fan states that Vinci "fell victim to those individuals jealous of his genius labeled him a man who did not finish his commissions as the [Gran Cavallo] was meant to be made of bronze, not clay."⁶ Another fan claims that the payment terms were so complex that he probably wouldn’t have received any compensation anyway. So get bored and leave-thankfully other artists, like Vincent van Gogh or Michelangelo, had a different attitude and struggled to complete their works out of passion and love.

Da Vinci Was Not a Mathematician

Although I’ve dabbled in art and art history, I am not an expert. However, I am an expert in mathematics, science, and engineering, having had a rigorous education in these fields and having worked for several decades in them. I’ve known true brilliant people in these areas. To my knowledge Leonardo da Vinci never wrote down an equation, even one as simple as basic algebra. He just didn’t seem to understand math⁷. Some credit him for understanding the golden ratio, but the golden ratio is simply two numbers-a width and a length-and had been known at least since the days of the Greek sculptor and mathematician Phidias, a thousand years before da Vinci⁸. Da Vinci came up with interesting mathematical ideas but never investigated one and never proved one. He spat out interesting possibilities in his notebooks, using a notation that has not been deciphered. Very few, if any, of his "mathematical ideas" turned out to be correct⁹. In fact, search the books, the Internet, or entire libraries, and you won’t find a single, tiny original contribution that da Vinci made to mathematics.

Mathematicians don’t guess at their answers. They study various techniques, sometimes for years. They learn how to use multiple mathematical models to find a solution. They compare alternative ways of performing calculations. They generalize the problems to solve categories of problems. They test their answers and try to find fault in them, try to tear the solution apart. Only after this long effort born of creative spark but nurtured by perseverance do they create something worthy of being labeled genius. Da vinci was far from a mathematical genius and giving him the title of mathematician demeans those who have spent their lives examining the beauty of numbers and their relationships.

Da Vinci Was Not a Scientist

Scientists practice the scientific method. They come up with hypotheses based on observations or the works of others, but that’s simply the very beginning. Every curious child imagines reasons why the world works the way it does. Most of them are fantastic and some turn out to be true. Ancient people thought the world was flat, supported by tortoises. But even the ancient Greeks, two thousand years before da Vinci, created the scientific method used by Archimedes, Aristotle, Hippocrates, Ptolemy, and many others¹⁰. Roger Bacon, two hundred years before da Vinci, was making discoveries and promoting the scientific method¹¹. All that da Vinci did was write fantastic theories in his notebooks but never once devised experiments to test them. Had he done that, he would have found that most of his theories were completely wrong. Again, there is not a single known, novel scientific principle that can be attributed to da Vinci. But at that same time, real scientific geniuses like Nicolaus Copernicus were changing our understanding of the solar system forever. To call da Vinci a scientist is like calling a curious kindergartener a scientist. It is an insult to those real scientists who spend their lives not just observing and hypothesizing, but testing, poring over results, retesting, studying the works of others, refining their own work, creating new theories, and eventually giving us more knowledge about how the universe functions.

Da Vinci Was Not an Engineer

Da Vinci was often given credit for the inventions of others, simply drawing machines, bridges, weapons, and other devices that had been written up by others or actually built by others¹². In fact most of his so-called inventions including diving suits and flying machines had been drawn up extensively by others¹³. Scientist Roger Bacon had drawn plans for an ornithopter 200 years before da Vinci and flying machines had been discussed and drawn since ancient times¹⁴. Modern attempts to build even a single one of da Vinci’s inventions have all failed because da Vinci didn’t understand materials or forces or structures or math or any engineering requirements. He never built any of his inventions; he simply drew them and in a few cases built small, non-working models. Engineering requires a deep understanding of mathematics and science. It also requires testing and experimenting and calculating and retesting and improving, leading to eventual success. As Thomas Edison famously said, it is 1 percent inspiration and 99 percent perspiration. It requires more than just dreaming and drawing, which is as far as da Vinci ever got. Honoring da Vinci as an engineer, let alone a brilliant one, denigrates the accomplishments of those engineers who spend years planning and measuring and calculating and building and rebuilding and creating the wonderful inventions that simplify or improve our lives.

Give Credit Where Credit is Due

In summary, da Vinci was a great artist, debatably one of the best who ever lived. Certainly the most famous. But to call him an engineer, scientist, or mathematician, let alone a brilliant one, is simply not true and is an insult to those who devote their lives and their energies to these important human endeavors.

1. Marion Boddy-Evans, Painting in the Style of Old Masters: Sfumato and Chiaroscuro, retrieved July 26, 2011.
2. Seen with my own eyes, the bottom left corner was never completed.
3. Leonardo Da Vinci Paintings, Inventions & Biography!, retrieved July 26, 2011.
4. Adoration of the Magi,retrieved July 26, 2011.
5. Giorgio Vasari, Lives of Seventy of the most eminent Painters, Sculptors and Architects (of the Renaissance), 1550.
6. Leonardo Da Vinci Paintings, Inventions & Biography!, retrieved July 26, 2011.
7. How Not to Think Like Leonardo da Vinci, retrieved July 26, 2011.
8. The Beauty of the Golden Ratio, retrieved July 26, 2011.
9. Dirk Huylebrouk, Lost in Triangulation: Leonardo da Vinci’s Mathematical Slip-Up, retrieved July 26, 2011.
10. Norman W. Edmund, Scientific Method History, retrieved July 26, 2011.
11. Brian Clegg, Review – The First Scientist, retrieved July 26, 2011.
12. Web Gallery of Art, Drawings of engineering themes, retrieved July 26, 2011.
13. Leonardo: the Man, His Machines, retrieved July 26, 2011.
14. Ornithopter Flying Machines: The Ancient Origins of an Invention, retrieved July 26, 2011.