@article{DAN_1965_161_3_a18,
     author = {V. D. Zakharov},
     title = {A physical characteristic of {Einsteinian} spaces of the second degenerate type in the {Petrov} classification},
     journal = {Doklady Akademii Nauk},
     pages = {563--565},
     publisher = {mathdoc},
     volume = {161},
     number = {3},
     year = {1965},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1965_161_3_a18/}
}