@article{10_4153_CMB_1961_008_3,
     author = {Ree, Rimhak},
     title = {On {Certain} {Pairs} of {Matrices} which do not {Generate} a {Free} {Group}},
     journal = {Canadian mathematical bulletin},
     pages = {49--52},
     year = {1961},
     volume = {4},
     number = {1},
     doi = {10.4153/CMB-1961-008-3},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1961-008-3/}
}