Some references to the state of the data world in the 70s is found Codd’s initial paper itself: https://www.seas.upenn.edu/~zives/03f/cis550/codd.pdf.

I strongly recommend everyone pick up basic set theory notation so that you can read seminal papers like these. There is so much amazing information in them, yet they’re treated as if they’re incomprehensible. You can understand the relational model with undergraduate-level discrete math and set theory knowledge.

These are the papers that formed our industry. Let’s not forget them.