@article{GDZPPN002413647, title = {Free Products of Hopf Groups.}, journal = {Mathematische Zeitschrift}, volume = {135}, year = {1973}, pages = {69-72}, zbl = {0274.20040}, url = {http://dml.mathdoc.fr/item/GDZPPN002413647} }
Newman, M.F.; Sichler, Jiri. Free Products of Hopf Groups.. Mathematische Zeitschrift, Tome 135 (1973) pp. 69-72. http://gdmltest.u-ga.fr/item/GDZPPN002413647/