@article{1183539469, author = {Schwarz, Gerald W.}, title = {Covering smooth homotopies of orbit spaces}, journal = {Bull. Amer. Math. Soc.}, volume = {83}, number = {6}, year = {1977}, pages = { 1028-1030}, language = {en}, url = {http://dml.mathdoc.fr/item/1183539469} }
Schwarz, Gerald W. Covering smooth homotopies of orbit spaces. Bull. Amer. Math. Soc., Tome 83 (1977) no. 6, pp. 1028-1030. http://gdmltest.u-ga.fr/item/1183539469/