PC1601LRS-GSO-B is covered by this 140 KB PDF datasheet, a character display module coded in the Powertip style for a 16 by 1 format.

AT command reference for the SIM900 GSM/GPRS module, provided as a 1.53 MB PDF. The manual lists the commands used to control calls, SMS, network registration, GPRS data…

Comparison document describing the differences between the SIM900 and SIM300 GSM modules, a 958 KB PDF.