@article{DE_1998_34_6_a2,
     author = {N. A. Izobov},
     title = {On the existence of a linear {Pfaffian} system with a countable number of distinct characteristic sets of solutions},
     journal = {Differencialʹnye uravneni\^a},
     pages = {735--743},
     publisher = {mathdoc},
     volume = {34},
     number = {6},
     year = {1998},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1998_34_6_a2/}
}