@article{DAN_1986_289_5_a12,
     author = {R. Martinez Brunet and A. V. Popov},
     title = {Focal spot structure on an inhomogeneous sphere},
     journal = {Doklady Akademii Nauk},
     pages = {1079--1083},
     publisher = {mathdoc},
     volume = {289},
     number = {5},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1986_289_5_a12/}
}