@article{DE_1988_24_9_a14,
     author = {P. I. Plotnikov and L. N. Yungerman},
     title = {Periodic solutions of a weakly nonlinear wave equation with an irrational relation of period to interval length},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1599--1607},
     publisher = {mathdoc},
     volume = {24},
     number = {9},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1988_24_9_a14/}
}