@article{DE_1975_11_11_a3,
     author = {V. A. Erovenko},
     title = {Lacunae in the spectrum of a fourth order differenetial operator with periodic coefficients},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1942--1948},
     publisher = {mathdoc},
     volume = {11},
     number = {11},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_11_a3/}
}