@article{DE_1966_2_7_a7,
     author = {A. N. Erugin},
     title = {Analytic structure of the solution of a differential equation with nonholomorphic right side in the case of a center or focus},
     journal = {Differencialʹnye uravneni\^a},
     pages = {934--942},
     year = {1966},
     volume = {2},
     number = {7},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1966_2_7_a7/}
}