@article{DE_1993_29_6_a16,
     author = {V. V. Amel'kin and Z. D. Ching},
     title = {Strong isochronism of the center of dynamical systems with incomplete polynomials of the third degree},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1057--1060},
     year = {1993},
     volume = {29},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1993_29_6_a16/}
}