Where can I get a good M4 GTS service manual?

[Gomeler]

Per the title, does anyone know of a service manual for the GTS that they're happy with? I maintain my track toys after finding far too many fasteners loose after various services, and I'd like a physical resource for torque specs and service procedures. I'm sure a regular F82 manual would work for most things, but some stuff like the front suspension and such would be nice to not have to research if I have it in pieces on the garage floor.