1. "Seminar on Transformation Groups,";A. Borel;Annals of Mathematics Studies,1960
2. Une théorie de Morse pour les systèmes hamiltoniens convexes,;I. Ekeland;Ann. IHP. Anal. non Linéaire,1984
3. "Convexity Methods in Hamiltonian Mechanics,";I. Ekeland;Ergebnisse der Mathematik und ihrer Grenzgebiete (3) [Results in Mathematics and Related Areas (3)],1990
4. Convex Hamiltonian energy surfaces and their closed trajectories,;I. Ekeland;Comm. Math. Phys.,1987
5. Multiplicité des trajectoires fermées d'un systéme hamiltoniens convexes,;I. Ekeland;Ann. IHP. Anal. non Linéaire,1987