@article{IM2_1982_19_2_a0,
     author = {S. I. Adian},
     title = {Normal subgroups of free periodic groups},
     journal = {Izvestiya. Mathematics },
     pages = {215--229},
     publisher = {mathdoc},
     volume = {19},
     number = {2},
     year = {1982},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1982_19_2_a0/}
}