Resource Recommendations to systematically develop a foundation via Self study in Astrophysics/Astronomy? had the resource (25 questions) tag which I didn't see. Instead I just added the reference-request (20 questions) tag.
Now it has both.
reference-request has no usage guidance, but resource says:
Questions asking "What is a good book about X?" or more generally, "What should I read to learn about X?", typically where there is not a single authoritative reference. Also requests for multimedia, like video lectures.
Question: What is the difference between resource and reference-request tags? Do we need both? What is good usage guidance for reference-request that defines it and differentiates it from the other?