Here is the documentation for the calculator:
HP 48G Series Quick Start Guide:
http://www.hpcalc.org/details.php?id=6402
HP 48G Series User's Guide:
http://www.hpcalc.org/details.php?id=3937
HP 48G Series Advanced User's Reference Manual:
http://www.hpcalc.org/details.php?id=6036
Note: The Advanced User's reference was NOT provided with the calculator. You would have to buy it separate. Now you can download it for free.