@article{TM_1999_227_a18,
     author = {S. I. Pokhozhaev},
     title = {The {Existence} and {Nonexistence} of {Periodic} {Solutions} to {Certain} {Nonlinear} {Hyperbolic} {Equations}},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {260--285},
     publisher = {mathdoc},
     volume = {227},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1999_227_a18/}
}