@article{GDZPPN00247347X, title = {An Example in Singular Perturbations.}, journal = {Monatshefte f\"ur Mathematik}, volume = {66}, year = {1962}, pages = {123-127}, zbl = {0201.14401}, url = {http://dml.mathdoc.fr/item/GDZPPN00247347X} }
Erdélyi, A. An Example in Singular Perturbations.. Monatshefte für Mathematik, Tome 66 (1962) pp. 123-127. http://gdmltest.u-ga.fr/item/GDZPPN00247347X/