@article{MS2_1975__36_166414,
     author = {Richard Randell},
     title = {Index invariants of orbit spaces.},
     journal = {Mathematica Scandinavica},
     pages = {264--271},
     publisher = {mathdoc},
     volume = {36},
     year = {1975},
     zbl = {0306.58015},
     url = {http://geodesic.mathdoc.fr/item/MS2_1975__36_166414/}
}