Teplins’kyi, O. Y. (2010). Examples of $C^1$-smoothly conjugate diffeomorphisms of the circle with break that are not $C^{1+γ}$ -smoothly conjugate. Ukrains’kyi Matematychnyi Zhurnal, 62(8), 1092–1105. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/2939