You should probably start with Brenda S Baker's work at Bell Labs: http://www.cs.ucdavis.edu/~devanbu/teaching/289/Schedule_fil... references the final result.

Baker's alumni web page: http://cm.bell-labs.com/cm/cs/who/bsb/index.html

It's unfortunate that Baker's "dup" and "pdiff" haven't gotten the open source treatment, or at least if they have, they're not widespread. SCO could have saved themselves a lot of lawyer's fees by running "dup" over SysV and Linux sources to see what's similar.