GroupBy: split-apply-combine, The pandas development team, 2024 - The official user guide section explaining core concepts of grouping data in pandas and demonstrating various aggregation techniques, including applying multiple functions and named aggregations.
pandas.DataFrameGroupBy.agg, The pandas development team, 2024 - The official API documentation for the agg() method on GroupBy objects, detailing its parameters and different usage patterns for applying multiple aggregations.
Python for Data Analysis, Wes McKinney, 2022 (O'Reilly Media) - A foundational text on data analysis with Python and pandas, authored by the creator of pandas. It comprehensively covers data grouping and aggregation techniques.