@article{IM2_2000_64_5_a7,
     author = {P. V. Yagodovskii},
     title = {Linear deformations of discrete groups and constructions of multivalued groups},
     journal = {Izvestiya. Mathematics},
     pages = {1065--1089},
     year = {2000},
     volume = {64},
     number = {5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2000_64_5_a7/}
}