@article{IM_1976__31_142357,
     author = {Reinhard Schultz},
     title = {Differentiable {Group} {Actions} on {Homotopy} {Spheres.} {I.} {Differential} {Structure} and the {Knot} {Invariant.}},
     journal = {Inventiones mathematicae},
     pages = {105--128},
     year = {1976},
     volume = {31},
     zbl = {0335.57025},
     url = {http://geodesic.mathdoc.fr/item/IM_1976__31_142357/}
}