Yann Bugeaud Christophe Reutenauer Samir Siksek A Sturmian sequence related to the uniqueness conjecture for Markoff numbers. 2864-2869 2009 410 Theor. Comput. Sci. 30-32 http://dx.doi.org/10.1016/j.tcs.2009.02.005 db/journals/tcs/tcs410.html#BugeaudRS09