@article{MZM_2004_76_3_a11,
     author = {I. A. Rudakov},
     title = {Periodic {Solutions} of a {Nonlinear} {Wave} {Equation} with {Nonconstant} {Coefficients}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {427--438},
     publisher = {mathdoc},
     volume = {76},
     number = {3},
     year = {2004},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2004_76_3_a11/}
}