@article{CMH_1981__56_139868,
     author = {Shing-Tung Yau and W.H. Meeks III},
     title = {The equivariant {Dehn's} lemma and loop theorem.},
     journal = {Commentarii mathematici Helvetici},
     pages = {225--239},
     publisher = {mathdoc},
     volume = {56},
     year = {1981},
     zbl = {0469.57005},
     url = {http://geodesic.mathdoc.fr/item/CMH_1981__56_139868/}
}