@article{1183487067, author = {Graustein, W. C.}, title = {An invariant of a general transformation of surfaces}, journal = {Bull. Amer. Math. Soc.}, volume = {32}, number = {5}, year = {1926}, pages = { 357-364}, language = {en}, url = {http://dml.mathdoc.fr/item/1183487067} }
Graustein, W. C. An invariant of a general transformation of surfaces. Bull. Amer. Math. Soc., Tome 32 (1926) no. 5, pp. 357-364. http://gdmltest.u-ga.fr/item/1183487067/