@article{DAN_1966_169_3_a12,
     author = {G. A. Sokolik and N. P. Konopleva},
     title = {Wave field equations covariant with an $n$-dimensional substantial unimodular group},
     journal = {Doklady Akademii Nauk},
     pages = {539--542},
     publisher = {mathdoc},
     volume = {169},
     number = {3},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1966_169_3_a12/}
}