DataFrame.join, pandas development team, 2023 - Official documentation for the DataFrame.join method, explaining its parameters, behavior, and examples.
pandas.merge, pandas development team, 2023 - Official documentation for the general-purpose pandas.merge function, which underpins DataFrame.join and offers broader combination capabilities.
Python for Data Analysis, Wes McKinney, 2022 (O'Reilly Media) - 3rd edition. A comprehensive guide by the creator of Pandas, offering foundational knowledge on data manipulation, including detailed discussions on joining and merging DataFrames.