Valérie Berthé Aldo de Luca Christophe Reutenauer On an involution of Christoffel words and Sturmian morphisms. 535-553 2008 29 Eur. J. Comb. 2 http://dx.doi.org/10.1016/j.ejc.2007.03.001 db/journals/ejc/ejc29.html#BertheLR08