@article{FORUM_1993__5_3_141697,
     author = {Bernd Baumann and Scoppola C.M.},
     title = {Canonical bases for normal subgroups of finitely generated free groups with finite abelian factor groups.},
     journal = {Forum mathematicum},
     pages = {23--32},
     publisher = {mathdoc},
     volume = {5},
     number = {3},
     year = {1993},
     zbl = {0799.20026},
     url = {http://geodesic.mathdoc.fr/item/FORUM_1993__5_3_141697/}
}