@article{IVM_1981_6_a4,
     author = {P. Ya. Grushko},
     title = {Some theorems on mappings of geometric structures},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {29--35},
     year = {1981},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1981_6_a4/}
}