1. M. L. Bialy and R. S. MacKay, Symplectic twist maps without conjugate points, Isr. J. Math., 141 (2004), 235–247.
2. G. D. Birkhoff, Surface transformations and their dynamical application, Acta Math., 43 (1920), 1–119.
3. A. Chenciner, La dynamique au voisinage d’un point fixe elliptique conservatif: de Poincaré et Birkhoff à Aubry et Mather., Astérisque, 1983/84(121–122) (1985), 147–170 (in French). [The dynamics at the neighborhood of a conservative elliptic fixed point: from Poincare and Birkhoff to Aubry and Mather] Seminar Bourbaki.
4. A. Chenciner, Systèmes dynamiques différentiables. Article à l’Encyclopedia Universalis.
5. G. Contreras and R. Iturriaga, Convex Hamiltonians without conjugate points, Ergod. Theory Dyn. Syst., 19(4) (1999), 901–952.