@article{10_4153_CMB_1984_055_6,
     author = {Gon\c{c}alves, Jairo Z.},
     title = {Free {Groups} in {Subnormal} {Subgroups} and the {Residual} {Nilpotence} of the {Group} of {Units} of {Groups} {Rings}},
     journal = {Canadian mathematical bulletin},
     pages = {365--370},
     year = {1984},
     volume = {27},
     number = {3},
     doi = {10.4153/CMB-1984-055-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1984-055-6/}
}