@article{DE_1997_33_5_a12,
     author = {E. K. Makarov},
     title = {On boundedness conditions for characteristic sets of solutions of linear multidimensional equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {653--657},
     publisher = {mathdoc},
     volume = {33},
     number = {5},
     year = {1997},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1997_33_5_a12/}
}