Codd, E. F. “A Relational Model of Data for Large Shared Data Banks.” Communications of the ACM 13, no. 6 (1970): 377–87. https://dl.acm.org/doi/10.1145/362384.362685.

Darwen, Hugh. “The Relational Model: Beginning of an Era.” IEEE Annals of the History of Computing 34, no. 4 (2012): 30–37. https://doi.org/10.1109/MAHC.2012.50.

Kent, William. “A Simple Guide to Five Normal Forms in Relational Database Theory.” Communications of the ACM 26, no. 2 (1983): 120–25. https://doi.org/10.1145/358024.358054.

Mackenzie, Adrian. “More Parts Than Elements: How Databases Multiply.” Environment and Planning D: Society and Space 30, no. 2 (2012): 335–50. https://doi.org/10.1068/d6710.

For reference

DB-Engines, “DB-Engines Ranking,” DB-Engines, December 2025, https://db-engines.com/en/ranking.