@article{1183524689,
author = {Erd\'elyi, A.},
title = {Singular perturbations},
journal = {Bull. Amer. Math. Soc.},
volume = {68},
number = {6},
year = {1962},
pages = { 420-424},
language = {en},
url = {http://dml.mathdoc.fr/item/1183524689}
}
Erdélyi, A. Singular perturbations. Bull. Amer. Math. Soc., Tome 68 (1962) no. 6, pp. 420-424. http://gdmltest.u-ga.fr/item/1183524689/