@article{MZ_1970__114_171291,
     author = {Daniel E. Cohen},
     title = {Ends and {Free} {Products} of {Groups.}},
     journal = {Mathematische Zeitschrift},
     pages = {9--18},
     publisher = {mathdoc},
     volume = {114},
     year = {1970},
     zbl = {0177.03501},
     url = {http://geodesic.mathdoc.fr/item/MZ_1970__114_171291/}
}