@article{10_4153_CJM_1975_029_5,
     author = {Brenner, J. L. and Macleod, R. A. and Olesky, D. D.},
     title = {Non-Free {Groups} {Generated} by {Two} 2 {X} 2 {Matrices}},
     journal = {Canadian journal of mathematics},
     pages = {237--245},
     year = {1975},
     volume = {27},
     number = {2},
     doi = {10.4153/CJM-1975-029-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1975-029-5/}
}