@article{10_1017_S0017089500003748,
     author = {Evans, Ronald J.},
     title = {Discrete free products of two complex cyclic matrix groups},
     journal = {Glasgow mathematical journal},
     pages = {69--80},
     year = {1979},
     volume = {20},
     number = {1},
     doi = {10.1017/S0017089500003748},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500003748/}
}