LASHKOV, A.; ZHIVKOV, A. Geometry and solutions of the planar problem of two centers of gravitation. Ann. Sofia Univ. Fac. Math. and Inf., [S. l.], v. 99, p. 129–136, 2009. Disponível em: https://stipendii.uni-sofia.bg/index.php/fmi/article/view/117. Acesso em: 12 dec. 2024.