@article{CMH_1977__52_139696,
     author = {R. Strebel},
     title = {A remark on subgroups of infinite index in {Poincar\'e} duality groups.},
     journal = {Commentarii mathematici Helvetici},
     pages = {317--324},
     publisher = {mathdoc},
     volume = {52},
     year = {1977},
     zbl = {0365.20040},
     url = {http://geodesic.mathdoc.fr/item/CMH_1977__52_139696/}
}