@article{IM_1978__45_142541,
     author = {E.R. Fadell and P.H. Rabinowitz},
     title = {Generalized {Cohomological} {Index} {Theories} for {Lie} {Group} {Actions} with an {Application} to {Bifurcation} {Questions} for {Hamiltonian} {Systems.}},
     journal = {Inventiones mathematicae},
     pages = {139--174},
     publisher = {mathdoc},
     volume = {45},
     year = {1978},
     zbl = {0403.57001},
     url = {http://geodesic.mathdoc.fr/item/IM_1978__45_142541/}
}