@article{AL_1969_8_1_a6,
     author = {A. L. Shmel'kin},
     title = {The lower central series of a free product of groups},
     journal = {Algebra i logika},
     pages = {129--137},
     publisher = {mathdoc},
     volume = {8},
     number = {1},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1969_8_1_a6/}
}