1. J. Liouville, Mémoire sur l’integration des équations différentielles du mouvement d’un nombre quelconque de points matériels. J. Math. Pures et Appl. 14, 257–299 (1849)
2. G. Morera, Sulla separazione delle variabili nelle equazioni del moto di un punto materiale su una superficie Atti. Sci. di Torino 16, 276–295 (1881)
3. A.M. Perelomov, Integrable Systems of Classical Mechanics and Lie Algebras (Birkhäuser, Basel 1990)
4. M.A. Gonzalez Leon, J. Mateos Guilarte, M. de la Torre Mayado, Orbits in the problem of two fixed centers on the sphere. Regul. Chaotic Dyn. 22, 520–542 (2017)
5. H.W. Killing, Die Mechanik in den nicht-euklidischen Raumformen. J. Reine Angew. Math. 98(1), 1–48 (1885)