Judy, there is a recommended reading list for the CPF (Certified Picture Framer) exam offered by the PPFA. These are all books that would be very nice to have in your reference library anyway, but some PPFA chapters (ours, for example) have lending collections available. You can get the list from the PPFA along with a study guide and some sample questions.
I'd say it is essential to read the study materials, even if you have had many years of experience. I've been a licensed driver for 36 years, but if I had to take the written test today without reading the driver's ed book, I'd probably have trouble.
The CPF certification is the most widely used and recognized for framers in the U.S. You'll occassionaly see the The Fine Art Trade Guild's, GCF, Guild Commended Framers (GCF) certification offered in this country.