pandas User Guide: Merge, join, concatenate and compare, The pandas development team, 2023 - Official documentation for Pandas functions like concat, merge, and join, offering detailed explanations and examples for combining DataFrames.
Python for Data Analysis, Wes McKinney, 2022 (O'Reilly Media) - A comprehensive book by the creator of Pandas, providing extensive guidance on data manipulation, including combining and reshaping DataFrames.