@article{1183494787,
author = {Michal, A. D.},
title = {Projective integral invariants attached to the trajectories of differential systems},
journal = {Bull. Amer. Math. Soc.},
volume = {37},
number = {12},
year = {1931},
pages = { 447-454},
language = {en},
url = {http://dml.mathdoc.fr/item/1183494787}
}
Michal, A. D. Projective integral invariants attached to the trajectories of differential systems. Bull. Amer. Math. Soc., Tome 37 (1931) no. 12, pp. 447-454. http://gdmltest.u-ga.fr/item/1183494787/