@article{MZM_1975_18_5_a12,
     author = {I. V. Bel'ko},
     title = {Degenerate {Riemannian} metrics},
     journal = {Matemati\v{c}eskie zametki},
     pages = {767--774},
     publisher = {mathdoc},
     volume = {18},
     number = {5},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1975_18_5_a12/}
}