@article{DE_1966_2_5_a6,
     author = {V. A. Tkachenko},
     title = {On conditions of discreteness of the spectrum of monomial differential operators},
     journal = {Differencialʹnye uravneni\^a},
     pages = {634--639},
     publisher = {mathdoc},
     volume = {2},
     number = {5},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1966_2_5_a6/}
}