@article{MAT_1968_12_4_a3,
     author = {P. M. Neumann and J. Wiegold},
     title = {Schreier varieties of groups},
     journal = {Matematika},
     pages = {42--49},
     year = {1968},
     volume = {12},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MAT_1968_12_4_a3/}
}