Isaac A. Garcia, Hector Giacomini, Jaume Giné, Jaume Llibre. Analytic nilpotent centers as limits of nondegenerate centers revisited.
Journal of Mathematical Analysis and Applications, Elsevier, 2016, 441, pp.893-899.
⟨10.1016/j.jmaa.2016.04.046⟩.
⟨hal-01309525⟩