R. H. Battin, An Introduction to the Mathematics and Methods of Astrodynamics, 1999.
DOI : 10.2514/4.861543

A. I. Neishtadt, Averaging, passage through resonances, and capture into resonance in two-frequency systems, Russian Mathematical Surveys, vol.69, issue.5, pp.771-843, 2014.
DOI : 10.1070/RM2014v069n05ABEH004917

J. A. Sanders and F. Verhulst, Averaging Methods in Nonlinear Dynamical Systems, 1985.
DOI : 10.1007/978-1-4757-4575-7