@article{MV_1957_9_3-4_a2,
     author = {I. Petrovskij},
     title = {O \v{c}isle predel'nyh ciklov obyknovennogo differencial'nogo uravnenia, u kotorogo pravaa             \v{c}ast' est' otno\v{s}enie dvuh mnogo\v{c}lenov},
     journal = {Matemati\v{c}ki vesnik},
     pages = {161 },
     publisher = {mathdoc},
     volume = {9},
     number = {3-4},
     year = {1957},
     url = {http://geodesic.mathdoc.fr/item/MV_1957_9_3-4_a2/}
}