@article{DAN_1975_221_6_a13,
     author = {L. A. Ostrovsky and A. M. Sutin},
     title = {Focusing of acoustic waves of finite amplitude},
     journal = {Doklady Akademii Nauk},
     pages = {1300--1303},
     publisher = {mathdoc},
     volume = {221},
     number = {6},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1975_221_6_a13/}
}