In a December 1981 letter, the editor of Word Ways proposed the following challenge:
The September/October 1981 issue of Games magazine sponsored a contest to find the maximum number of four-letter mutually non-crashing words in boldface in Webster's Third (or inferred plurals of boldface). To my surprise, the winner came up with 21 words: abbe, baff, cleg, djin, eddy, frum, gnaw, huzz, isn't, jowl, Kthu, Lvov, myth, Omsk, PFCs, repp, skyr, Tchi, upgo, vild, Xtra. I'm now wondering if, with all the weird spellings in the OED, whether that dictionary might be used as a single source to equal or exceed this record.
"Non-Crashing Word Sets,"
Word Ways: Vol. 15
, Article 15.
Available at: http://digitalcommons.butler.edu/wordways/vol15/iss2/15