This page is mostly focused on turboprop information (so far).
Airplane Flying Handbook Ch 16, Turboprop Transition
Airplane Turbofan Engine Operation and Malfunctions – Basic Familiarization for Flight Crews
Airplane Turboprop Engines Basic Familiarization
Fundamentals of Gas Turbine Engines From the Commercial Aviation Safety Team (CAST)
See the variants and more here on P&WC website
PT6 DESCRIPTIVE COURSE AND GUIDE TO TROUBLESHOOTING
PT6A-Small Engine Propeller Control System
Garrett Engines
Garrett Engine Manual (TPE331)
Mike Kloch Aviation Consulting 