@article{IM2_1978_12_1_a0,
     author = {O. V. Mel'nikov},
     title = {Normal subgroups of free profinite groups},
     journal = {Izvestiya. Mathematics },
     pages = {1--20},
     publisher = {mathdoc},
     volume = {12},
     number = {1},
     year = {1978},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1978_12_1_a0/}
}