@article{DE_1978_14_9_a6,
     author = {L. A. Cherkas},
     title = {Conditions for a center for the equation $yy'=\sum_{i=0}^3 p_i(x)y^i$},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1594--1600},
     publisher = {mathdoc},
     volume = {14},
     number = {9},
     year = {1978},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1978_14_9_a6/}
}