@article{SM_1968_5_4_a0,
     author = {N. V. Efimov},
     title = {Differential criteria for homeomorphism of certain mappings with},
     journal = {Sbornik. Mathematics},
     pages = {475--488},
     year = {1968},
     volume = {5},
     number = {4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1968_5_4_a0/}
}