When the time comes more fully learn the Laws of the Game and prepare for your test/recertification, no document will serve a referee better than Guidelines for Referees in the Laws of the Game booklet. Page through it a couple of times a year, then give it a careful reading a day or two before your test. Knowing the Laws, and using the Guidelines will improve your score by at least 10 to 15 points, as often many of the questions asked are covered in this part of the Laws booklet.
https://ussoccer.app.box.com/s/xx3byxqgodqtl1h15865