Smith P. A singular perturbation method for saddle connections and subitarmonie of certain nonlinear differential equations with fixed saddle points. Rev. mat. complut. [Internet]. 1 de enero de 1990 [citado 25 de noviembre de 2024];3(1):89. Disponible en: https://doi.org/10.5209/rev_REMA.1990.v3.n1.18051