@article{MZ_1968__106_171021,
     author = {John Cossey},
     title = {On a {Problem} of {Hanna} {Neumann.}},
     journal = {Mathematische Zeitschrift},
     pages = {187--190},
     publisher = {mathdoc},
     volume = {106},
     year = {1968},
     zbl = {0174.04702},
     url = {http://geodesic.mathdoc.fr/item/MZ_1968__106_171021/}
}