@article{MZ_1972__127_171773,
     author = {Peter C. Oxley},
     title = {Ends and {Amalgamated} {Free} {Products} of {Groups.}},
     journal = {Mathematische Zeitschrift},
     pages = {265--272},
     publisher = {mathdoc},
     volume = {127},
     year = {1972},
     zbl = {0227.20010},
     url = {http://geodesic.mathdoc.fr/item/MZ_1972__127_171773/}
}