The following is directly quoted from the reference URL:
http://www.hpcalc.org/hp48/docs/faq/48faq-10.html
HP48 FAQ Section 10: Appendix B: GX Specific Information
"The G/GX comes with two manuals, a 'Quick Start Guide' for beginners, and a cost-cutting, slimmer owner's manual called the 'User's Guide' which has only 21 pages about programming, since HP figures that the huge majority of all 48 owners never program it anyway. The power users can buy the optional 'Advanced Users Reference Manual' (similar to the S/SX's 'Programmer's Reference Manual') which covers programming and the many commands that are not mentioned in the User's Guide. There is no 'Quick Reference Guide' like the S/SX came with, although the case still has a pocket for one.
Jim Donnelly has marketed a nice pocket guide, but it's too wide to fit in the case's pocket. The User's Guide is not spiral bound, but is made to open fully and last a long time, since it's not just glued but has sewn signatures like real books, and is printed on quality paper.
Another possibility is 'The HP 48G/GX Pocket Guide' by Chris Coffin and Thomas Dick (Grapevine Publications). It's 80 pages long, contains a complete command reference (with input/output stack diagrams), alpha keyboard description, system flag description, as well as examples of how to use various calculator features. This guide is designed to fit nicely in the pocket of the HP case."
Hope this info helps!
polarbear mike