Considering the enormous difficulties encountered in the construction of large word squares, it is not surprising that the first 15-square ever found should require unusual words from obscure sources. However, success was assured with the aid of the fearsome Zong computer, and the square, with all words carefully defined, is given below.
Wolpow, Edward R.
"A Ziticorumbatous 15-Square,"
Word Ways: Vol. 14
, Article 9.
Available at: http://digitalcommons.butler.edu/wordways/vol14/iss2/9