@article{MZM_1992_51_4_a4,
     author = {I. A. Kipriyanov and Yu. V. Zasorin},
     title = {Newton's principle for the wave equation},
     journal = {Matemati\v{c}eskie zametki},
     pages = {36--42},
     year = {1992},
     volume = {51},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1992_51_4_a4/}
}