I am not real good at reference material. I have various links to other web sites. Those are easy. I read a lot. Usually two books at a time. But I did miserably in English classes where I had to write papers with references. So here are a very few books that I think are helpful.
You can also look at the book rack at Camping World. They have most books that I could suggest.
Traveler’s Guide to the Firearms
Laws of the Fifty States, J. Scott Kappas,
Traveler’s Guide, Box 2156, Covington, KY 41012 (606) 491-8500