Christov, Ognyan. “Bifurcations of Invariant Manifolds in a Model in Rigid Body Dynamics”. Ann. Sofia Univ. Fac. Math. and Inf. 85 (December 12, 1993): 123–129. Accessed November 24, 2024. https://ftl5.uni-sofia.bg./index.php/fmi/article/view/460.