@article{IM_1974__23_142249,
     author = {K. Grove and H. Karcher and E.A. Ruh},
     title = {Group {Actions} and {Curvature.}},
     journal = {Inventiones mathematicae},
     pages = {31--48},
     year = {1974},
     volume = {23},
     zbl = {0271.53044},
     url = {http://geodesic.mathdoc.fr/item/IM_1974__23_142249/}
}