1. V.I. Arnold, Sur une propriété topologique des applications canoniques de la mécanique classique, C. R. Acad. Sci. Paris, 261 (1965), 3719–3722.
2. M. Chaperon, Quelques questions de géométrie symplectique, Séminaire Bourbaki, Astérisque, 1982/83 (1983), 231–249.
3. K.C. Chang, Infinite Dimensional Morse Theory and Multiple Solution Problem, Progress in Nonlinear Differential Equations and their Applications, volume 6, Birkhäuser, Boston, MA, 1993. https://doi.org/10.1007/978-1-4612-0385-8
4. C.C. Conley, E. Zehnder, The Birkhoff-Lewis fixed point theorem and a conjecture of V. I. Arnold, Invent. Math., 73 (1983), 33–49. https://doi.org/10.1007/BF01393824
5. O. Cornea, G. Lupton, J. Oprea, D. Tanré, Lusternik-Schnirelmann category, volume 103 of Mathematical Surveys and Monographs, American Mathematical Society, Providence, RI, 2003. https://doi.org/10.1007/978-1-4612-0385-8