@article{1077491745, author = {Roberts, J. H.}, title = {Two-to-one transformations}, journal = {Duke Math. J.}, volume = {6}, number = {1}, year = {1940}, pages = { 256-262}, language = {en}, url = {http://dml.mathdoc.fr/item/1077491745} }
Roberts, J. H. Two-to-one transformations. Duke Math. J., Tome 6 (1940) no. 1, pp. 256-262. http://gdmltest.u-ga.fr/item/1077491745/