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@article{MAT_1968_12_5_a4, author = {Ya. Ihara}, title = {Discrete subgroups of $\mathrm{PL}(2,k_\mathfrak p)$}, journal = {Matematika}, pages = {131--138}, publisher = {mathdoc}, volume = {12}, number = {5}, year = {1968}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MAT_1968_12_5_a4/} }
Ya. Ihara. Discrete subgroups of $\mathrm{PL}(2,k_\mathfrak p)$. Matematika, Tome 12 (1968) no. 5, pp. 131-138. http://geodesic.mathdoc.fr/item/MAT_1968_12_5_a4/