Anil (WW 41 (2) p223) asks whether there is a theory which explains how the periodic behaviour of Fibconacci letter-sequences works. The answer is yes, there is indeed such a theory, and it has many other applications, both mathematical and practical. Though this theory has nothing to do with words, I hope that readers will he interested in its results. However, most of the proofs will be beyond the scope of this article.
"Properties of Sequences,"
Word Ways: Vol. 42
, Article 15.
Available at: https://digitalcommons.butler.edu/wordways/vol42/iss1/15