To my mind, an ideal hardcore logology project should satisfy two conditions: (1) it should be hard enough to force the investigator out of the cozy Webster's Second Unabridged (NI2) and Third Unabridged (NI3) nook, and (2) it should promise complete success -- every last hole filled -- with persistence. AN excellent example is the problem of finding words beginning with each of the 676 possible two-letter combinations, or bigrams. This problem is covered in the section "Zero Redundancy" (ZR) in Dmitri Borgmann's Beyond Language (Scribner's, 1967). Unfortunately, while Dmitri claimed words for 629 of the combinations, he listed only 547 of them and has no record left of most of the remainder.
Cohen, Philip M.
Word Ways: Vol. 8
, Article 8.
Available at: https://digitalcommons.butler.edu/wordways/vol8/iss2/8