In 1978, Loren Kohnfelder invented digital certificates while working on his MIT undergraduate thesis. Today, digital certificates are widely used to distribute the public keys that are the basis of the Internet's encryption system. This is important stuff! But when I tried to find an online copy of Kohnfelder's 1978 manuscript, I came up blank. According to the MIT Libraries' catalog, there were just two copies in the system: a microfiche somewhere in Barker Engineering Library, and a "noncirculating" copy in the Institute Archives.

Google couldn't find anything. Nor could CiteSeer, an online database of scholarly papers in computer science. Finally I found an e-mail address for Kohnfelder himself in MIT's online alumni database. A few hours later, he informed me that a scanned copy of his thesis could be downloaded from the website theses.mit.edu. And as it turns out, a copy of Kohnfelder's thesis has also been entered into DSpace, the big digital-repository project that MIT Libraries and Hewlett-Packard started back in 2002. That copy is indexed by Google Scholar, Google's academic search engine. But I hadn't thought to check there.