@article{DE_1983_19_3_a20,
     author = {P. G. Lasy},
     title = {On the theory of stability in the first approximation of completely integrable {Pfaffian} systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {529--532},
     publisher = {mathdoc},
     volume = {19},
     number = {3},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1983_19_3_a20/}
}