Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DE_1985_21_2_a10, author = {D. Kh. Safarov}, title = {Systems of first-order partial differential equations of composite type}, journal = {Differencialʹnye uravneni\^a}, pages = {272--276}, publisher = {mathdoc}, volume = {21}, number = {2}, year = {1985}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1985_21_2_a10/} }
D. Kh. Safarov. Systems of first-order partial differential equations of composite type. Differencialʹnye uravneniâ, Tome 21 (1985) no. 2, pp. 272-276. http://geodesic.mathdoc.fr/item/DE_1985_21_2_a10/