@article{IM_1981__65_142857,
     author = {William Browder and Wu-Chung Hsiang},
     title = {G-actions and the {Fundamental} {Group.}},
     journal = {Inventiones mathematicae},
     pages = {411--424},
     publisher = {mathdoc},
     volume = {65},
     year = {1981},
     zbl = {0519.57034},
     url = {http://geodesic.mathdoc.fr/item/IM_1981__65_142857/}
}