@article{MAN_1973__206_162503,
     author = {Heiner Zieschang},
     title = {On the {Homeotopy} {Groups} of {Surfaces.}},
     journal = {Mathematische Annalen},
     pages = {1--22},
     publisher = {mathdoc},
     volume = {206},
     year = {1973},
     zbl = {0248.55001},
     url = {http://geodesic.mathdoc.fr/item/MAN_1973__206_162503/}
}