@article{IM_1973__22_142244,
     author = {J. Levine},
     title = {Semi-Free {Circel} {Actions} on {Spheres.}},
     journal = {Inventiones mathematicae},
     pages = {161--186},
     publisher = {mathdoc},
     volume = {22},
     year = {1973},
     zbl = {0266.57010},
     url = {http://geodesic.mathdoc.fr/item/IM_1973__22_142244/}
}