Classification of Normal Congruence Subgroups of the Modular Group
1988 ◽
Vol 64
(5)
◽
pp. 167-169
1963 ◽
Vol 69
(5)
◽
pp. 719-721
◽
1988 ◽
Vol 64
(6)
◽
pp. 205-207
1991 ◽
Vol 1991
(414)
◽
pp. 113-116
◽
2012 ◽
Vol 08
(04)
◽
pp. 983-992
◽
1965 ◽
Vol 16
(4)
◽
pp. 831-831
◽
2020 ◽
Vol 12
(1)
◽
pp. 108-111
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