We define Markoff words as certain factors appearing in bi-infinite words satisfying the Markoff condition. We prove that these words coincide with central words, yielding a new characterization of Christoffel words. Key words: combinatorial problems, Markoff condition, balanced words, central words, Christoffel words, palindromes. 1991 MSC: 68R15.
Amy Glen, Aaron Lauve, Franco V. Saliola