@article{MOMA_1962__66_177157,
     author = {A. Erd\'elyi},
     title = {An {Example} in {Singular} {Perturbations.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {123--127},
     publisher = {mathdoc},
     volume = {66},
     year = {1962},
     zbl = {0201.14401},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1962__66_177157/}
}