@article{INTG_1986_18_a0,
     author = {P. Ya. Grushko},
     title = {Mappings of geometric structures},
     journal = {Itogi Nauki i Tekhniki. Seriya Problemy Geometrii. Trudy Geometricheskogo Seminara},
     pages = {3--23},
     year = {1986},
     volume = {18},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/INTG_1986_18_a0/}
}