On a theorem by Leon Greenberg
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- by A. W. Mason PDF
- Proc. Amer. Math. Soc. 23 (1969), 18-23 Request permission
References
- L. Greenberg, Note on normal subgroups of the modular group, Proc. Amer. Math. Soc. 17 (1966), 1195–1198. MR 199274, DOI 10.1090/S0002-9939-1966-0199274-4
- M. I. Knopp and M. Newman, Congruence subgroups of positive genus of the modular group, Illinois J. Math. 9 (1965), 577–583. MR 181675 A. M. Macbeath, Fuchsian groups, Lectures at Queen’s College, Dundee, Scotland, 1961.
- A. W. Mason, Lattice subgroups of free congruence groups, Glasgow Math. J. 10 (1969), 106–115. MR 276365, DOI 10.1017/S0017089500000641
- Morris Newman, Free subgroups and normal subgroups of the modular group, Illinois J. Math. 8 (1964), 262–265. MR 159865
- Morris Newman, Classification of normal subgroups of the modular group, Trans. Amer. Math. Soc. 126 (1967), 267–277. MR 204375, DOI 10.1090/S0002-9947-1967-0204375-3
- Klaus Wohlfahrt, An extension of F. Klein’s level concept, Illinois J. Math. 8 (1964), 529–535. MR 167533
Additional Information
- © Copyright 1969 American Mathematical Society
- Journal: Proc. Amer. Math. Soc. 23 (1969), 18-23
- MSC: Primary 30.49; Secondary 10.00
- DOI: https://doi.org/10.1090/S0002-9939-1969-0245794-6
- MathSciNet review: 0245794