@article{AL_1970_9_4_a2,
     author = {Yu. M. Gorchakov and V. M. Levchuk},
     title = {The approximation of free groups},
     journal = {Algebra i logika},
     pages = {415--421},
     publisher = {mathdoc},
     volume = {9},
     number = {4},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1970_9_4_a2/}
}