@article{MZ_1983__184_173359,
     author = {B\"arbel Wicha-Krause},
     title = {On {Embedded} {2-Spheres} in {3-Manifolds.}},
     journal = {Mathematische Zeitschrift},
     pages = {235--244},
     publisher = {mathdoc},
     volume = {184},
     year = {1983},
     zbl = {0507.57008},
     url = {http://geodesic.mathdoc.fr/item/MZ_1983__184_173359/}
}