@article{GDZPPN002407604, title = {The Hopf Property of Free Products.}, journal = {Mathematische Zeitschrift}, volume = {114}, year = {1970}, pages = {325-339}, zbl = {0204.34205}, url = {http://dml.mathdoc.fr/item/GDZPPN002407604} }
Neumann, Hanna; Dey, I.M.S. The Hopf Property of Free Products.. Mathematische Zeitschrift, Tome 114 (1970) pp. 325-339. http://gdmltest.u-ga.fr/item/GDZPPN002407604/