@article{VMUMM_1985_4_a18,
     author = {I. A. Rudakov},
     title = {Free nonlinear vibrations of a string},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {80--83},
     year = {1985},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1985_4_a18/}
}