To clarify, Nick Johnson is referring to the original paper on the topic ("Some approaches to best match file searching" by Burkhard and Keller in 1973). It's a common frustration that ACM archives are not freely available to the public.

In the comments, "Sarah" notes that the paper can be found here:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.160...

BTW, Nick's Blog often has gems and is well worth a regular read.