The February 1991 Word Ways introduced the concept of a word string network: a set of n-letter words connected by directed links. Word A is joined to Word B by a directed link if Word B is formed by removing the first letter of WOrd A and placing a letter (not neceassrily the same one) at the end of Word A (such as TEA to EAT, or SAFRI ato ARID). Note that a link does not connect EAT to ATE to TEA.
Eckler, A. Ross
"Directed Word Chain Networks (Part 1),"
Word Ways: Vol. 24
, Article 9.
Available at: http://digitalcommons.butler.edu/wordways/vol24/iss3/9