@article{GDZPPN00210542X,
title = {Subgroups of finite index in nilpotent groups.},
journal = {Inventiones mathematicae},
volume = {93},
year = {1988},
pages = {185-224},
zbl = {0651.20040},
url = {http://dml.mathdoc.fr/item/GDZPPN00210542X}
}
Segal, D.; Grunewald, F.J.; Smith, G.C. Subgroups of finite index in nilpotent groups.. Inventiones mathematicae, Tome 93 (1988) pp. 185-224. http://gdmltest.u-ga.fr/item/GDZPPN00210542X/