@article{IVM_2017_9_a3,
     author = {A. E. Kuvaev and E. V. Sokolov},
     title = {Necessary conditions of the approximability of generalized free products and},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {36--47},
     year = {2017},
     number = {9},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_2017_9_a3/}
}