@article{DE_1967_3_8_a0,
     author = {S. T. Zavalishchin},
     title = {Periodic generalized orbits},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1231--1239},
     publisher = {mathdoc},
     volume = {3},
     number = {8},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1967_3_8_a0/}
}