In the November 1979 Word Ways there was an interesting challenging article by Dmitri A. Borgmann called "Palindromes: The Rotas Square."
I was glad to see the Master Logologist return to the problem of the Sator square, about which he said in his Language on Vacation (p. 208), "The treatment we have given the 'Sator' square is far from adequate, partly for lack of space, partly because we don't happen to care for it ...."
Partridge, Harry B.
"The Sator Square Revisited,"
1, Article 5.
Available at: http://digitalcommons.butler.edu/wordways/vol13/iss1/5