@article{MZ_1991__207_2_174265,
     author = {D.D. Long and G.A. Niblo},
     title = {Subgroup separability and 3-manifold groups.},
     journal = {Mathematische Zeitschrift},
     pages = {209--216},
     publisher = {mathdoc},
     volume = {207},
     number = {2},
     year = {1991},
     zbl = {0711.57002},
     url = {http://geodesic.mathdoc.fr/item/MZ_1991__207_2_174265/}
}