@article{MZ_1964__85_170303,
     author = {I.M.S. Dey},
     title = {Free products of {Hopf} groups.},
     journal = {Mathematische Zeitschrift},
     pages = {274--284},
     publisher = {mathdoc},
     volume = {85},
     year = {1964},
     zbl = {0126.04803},
     url = {http://geodesic.mathdoc.fr/item/MZ_1964__85_170303/}
}