The official REST API tutorial on Wikipedia: https://en.wikipedia.org/wiki/Representational_state_transfer
The official REST API documentation on Postman: https://www.postman.com/blog/what-is-a-rest-api/
The REST API tutorial on FreeCodeCamp: https://www.freecodecamp.org/news/a-complete-guide-to-apis-and-rest-apis-a11477a9f2c4
The REST API basics on Codecademy: https://www.codecademy.com/learn/learn-api-design
The REST API tutorial on RESTful API: https://restful-api.com/tutorial/