@article{MZ_1983__184_173342,
     author = {John R. Stallings},
     title = {Surfaces in {Three-Manifolds} and {Non-Singular} {Equations} in {Groups.}},
     journal = {Mathematische Zeitschrift},
     pages = {1--18},
     publisher = {mathdoc},
     volume = {184},
     year = {1983},
     zbl = {0496.57006},
     url = {http://geodesic.mathdoc.fr/item/MZ_1983__184_173342/}
}