@article{1077473734,
author = {Friedrichs, K. O. and Wasow, W. R.},
title = {Singular perturbations of non-linear oscillations},
journal = {Duke Math. J.},
volume = {13},
number = {1},
year = {1946},
pages = { 367-381},
language = {en},
url = {http://dml.mathdoc.fr/item/1077473734}
}
Friedrichs, K. O.; Wasow, W. R. Singular perturbations of non-linear oscillations. Duke Math. J., Tome 13 (1946) no. 1, pp. 367-381. http://gdmltest.u-ga.fr/item/1077473734/