@article{DAN_1971_198_2_a7,
     author = {I. T. Kiguradze},
     title = {On the periodic solutions of a system of ordinary differential equations with singularities},
     journal = {Doklady Akademii Nauk},
     pages = {286--289},
     publisher = {mathdoc},
     volume = {198},
     number = {2},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_198_2_a7/}
}