@article{SM_1969_9_4_a4,
     author = {V. V. Filippov},
     title = {Quotient spaces and multiplicity of a~base},
     journal = {Sbornik. Mathematics},
     pages = {487--496},
     year = {1969},
     volume = {9},
     number = {4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1969_9_4_a4/}
}