Steps To Reproduce

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Expected Behavior

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Actual Behavior

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Additional Information

Reported by Chengyang Bao via David Loeffler:

typo in the Sage reference manual: in the class docstring for sage.modular.arithgroup.congroup_gammaH.GammaH_class, the formula "a, b \in H" should say "a, d \in H".

(See https://doc.sagemath.org/html/en/reference/arithgroup/sage/modular/arithgroup/congroup_gammaH.html#sage.modular.arithgroup.congroup_gammaH.GammaH_class).

Environment

- **OS**:
- **Sage Version**:

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide