@article{DAN_1963_150_5_a17,
     author = {I. D. Novikov and L. M. Ozernoi},
     title = {Propagation of light outside and inside a singular {Schwarzschild} sphere},
     journal = {Doklady Akademii Nauk},
     pages = {1019--1021},
     publisher = {mathdoc},
     volume = {150},
     number = {5},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1963_150_5_a17/}
}