Congruence testing for odd subgroups of the modular group
2014 ◽
Vol 17
(1)
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pp. 206-208
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AbstractWe give a computationally effective criterion for determining whether a finite-index subgroup of $\mathrm{SL}_2(\mathbf{Z})$ is a congruence subgroup, extending earlier work of Hsu for subgroups of $\mathrm{PSL}_2(\mathbf{Z})$.
2012 ◽
Vol 22
(03)
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pp. 1250026
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2005 ◽
Vol 71
(3)
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pp. 399-404
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2013 ◽
Vol 156
(1)
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pp. 115-121
2013 ◽
Vol 34
(3)
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pp. 837-853
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1998 ◽
Vol 41
(2)
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pp. 303-313
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2011 ◽
Vol 21
(04)
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pp. 547-574
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