@article{DE_2001_37_5_a5,
     author = {N. A. Izobov and E. N. Krupchik},
     title = {Necessary {Properties} of {Boundary} {Degree} {Sets} of {Solutions} to {Linear} {Pfaff} {Systems}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {616--627},
     publisher = {mathdoc},
     volume = {37},
     number = {5},
     year = {2001},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2001_37_5_a5/}
}