The following combinatorial result from Fine and Wilf (1995) is essential to obtaining these results : If (w) is a word with periods (p) and (q) that is if (z=v) and (g=r) for some suffixes (u') of (u) and (v') of (v) then (w) also has a period gcd(p,q) the greatest common divisor of its two periods-provided (w) is of length at least p+q-gcd(p,q)