Deneva, Sonia. “ON NONHOLONOMIC PROBLEMS FOR THE MOTION OF RIGID BODY ON A ROUGH SURFACE”. Ann. Sofia Univ. Fac. Math. and Inf. 82, no. 2 (December 12, 1991): 111–134. Accessed November 22, 2024. https://annual.uni-sofia.bg/index.php/fmi/article/view/539.