@article{GDZPPN002353253, title = {Index invariants of orbit spaces.}, journal = {Mathematica Scandinavica}, volume = {36}, year = {1975}, pages = {264-271}, zbl = {0306.58015}, url = {http://dml.mathdoc.fr/item/GDZPPN002353253} }
Randell, Richard. Index invariants of orbit spaces.. Mathematica Scandinavica, Tome 36 (1975) pp. 264-271. http://gdmltest.u-ga.fr/item/GDZPPN002353253/