@article{DE_1975_11_10_a21,
     author = {V. A. Erovenko},
     title = {$\lambda $-zones of instability for {Hill's} differential equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1890--1892},
     publisher = {mathdoc},
     volume = {11},
     number = {10},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_10_a21/}
}