LEAST PERIODS OF FACTORS OF INFINITE WORDS

We sh ow t h at any p osit ive int eger is t h e least p e rio d of afact or of t h e Thu e- Morse word . We also ch aract e rize t h e set of leastp erio d s of factors of a S turmian word. In particular, the corresp ondingset for t h e F ib on acci word is t h e set of Fib on acci nu mb ers. A s a by -pro duct of our resu lts, we give several n ew pro ofs an d tighten in gs ofwe ll- k n own p rop e rt ies of S t u rmian word s