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@article{MAN_1983__263_163727, author = {J.L. Brenner and R.C. Lyndon}, title = {Maximal {Nonparabolic} {Subgroups} of the {Modular} {Group.}}, journal = {Mathematische Annalen}, pages = {1--12}, publisher = {mathdoc}, volume = {263}, year = {1983}, zbl = {0491.20037}, url = {http://geodesic.mathdoc.fr/item/MAN_1983__263_163727/} }
J.L. Brenner; R.C. Lyndon. Maximal Nonparabolic Subgroups of the Modular Group.. Mathematische Annalen, Tome 263 (1983), pp. 1-12. http://geodesic.mathdoc.fr/item/MAN_1983__263_163727/