@article{MZ_1977__154_172511,
     author = {J.C. Lennox and D. Segal and S. Stonehewer},
     title = {The {Lower} {Central} {Series} of a {Join} of {Subnormal} {Subgroups.}},
     journal = {Mathematische Zeitschrift},
     pages = {85--90},
     publisher = {mathdoc},
     volume = {154},
     year = {1977},
     zbl = {0334.20017},
     url = {http://geodesic.mathdoc.fr/item/MZ_1977__154_172511/}
}