@article{DE_1977_13_2_a9,
     author = {V. M. Isakov},
     title = {The inverse problem of potential theory for hyperbolic equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {305--313},
     publisher = {mathdoc},
     volume = {13},
     number = {2},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_2_a9/}
}