pandas.DataFrame.quantile, The pandas development team, 2023 - Official documentation for calculating quantiles, which are used for percentiles and quartiles in Pandas.
pandas.DataFrame.describe, The pandas development team, 2023 - Official documentation for generating descriptive statistics, including quartiles, for Pandas DataFrames and Series.
OpenIntro Statistics, David M Diez, Christopher D Barr, Mine Çetinkaya-Rundel, 2023 (OpenIntro) - A comprehensive and freely available textbook covering foundational statistical concepts, including measures of location and spread like percentiles, quartiles, and IQR.