The Pears Word Games Society (PWGS) recognizes five versions of the same basic game, though its members tend to restrict themselves to only one of these, the smallest. The National Puzzlers' League (NPL) has also played Competitive Word Squares but to a playing format that makes high scoring almost impossible.
"Competitive Word Squares,"
Word Ways: Vol. 24
, Article 10.
Available at: http://digitalcommons.butler.edu/wordways/vol24/iss1/10