@article{DE_1971_7_6_a5,
     author = {K. K. Kammatov},
     title = {Oscillations in certain essentially nonlinear systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {997--1006},
     publisher = {mathdoc},
     volume = {7},
     number = {6},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_6_a5/}
}