@article{DAN_1993_332_4_a4,
     author = {\`E. G. Poznyak and A. G. Popov},
     title = {Lobachevskii geometry and equations of mathematical physics},
     journal = {Doklady Akademii Nauk},
     pages = {418--421},
     publisher = {mathdoc},
     volume = {332},
     number = {4},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1993_332_4_a4/}
}