@article{DE_1977_13_4_a21,
     author = {\`E. I. Grudo and L. F. Yanchuk},
     title = {Inequalities of {Gronwall,} {Bihari} and {Langenhop} type for {Pfaffian} systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {749--752},
     publisher = {mathdoc},
     volume = {13},
     number = {4},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_4_a21/}
}