@article{1077490197,
author = {Langer, Rudolph E.},
title = {The expansion theory of ordinary differential systems of the first order},
journal = {Duke Math. J.},
volume = {3},
number = {1},
year = {1937},
pages = { 383-393},
language = {en},
url = {http://dml.mathdoc.fr/item/1077490197}
}
Langer, Rudolph E. The expansion theory of ordinary differential systems of the first order. Duke Math. J., Tome 3 (1937) no. 1, pp. 383-393. http://gdmltest.u-ga.fr/item/1077490197/