Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DE_1974_10_8_a22, author = {Z. O. Mel'nik}, title = {Hyperbolic equations with multiple characteristics}, journal = {Differencialʹnye uravneni\^a}, pages = {1530--1532}, publisher = {mathdoc}, volume = {10}, number = {8}, year = {1974}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1974_10_8_a22/} }
Z. O. Mel'nik. Hyperbolic equations with multiple characteristics. Differencialʹnye uravneniâ, Tome 10 (1974) no. 8, pp. 1530-1532. http://geodesic.mathdoc.fr/item/DE_1974_10_8_a22/