@article{1077492258,
author = {Levine, Jack},
title = {Invariants of systems of second order linear differential
equations},
journal = {Duke Math. J.},
volume = {6},
number = {1},
year = {1940},
pages = { 298-311},
language = {en},
url = {http://dml.mathdoc.fr/item/1077492258}
}
Levine, Jack. Invariants of systems of second order linear differential equations. Duke Math. J., Tome 6 (1940) no. 1, pp. 298-311. http://gdmltest.u-ga.fr/item/1077492258/