[HECnet] DECnet Phase-III anywhere?

[Bob Armstrong]

   I have a need to set up a PDP-11 running DECnet Phase-III, preferably under RSX11M although I   d take RSTS in a pinch.   Not RT-11.     Have any of the install tapes or manuals been archived online?   Could anybody give me a hint or pointer?
  
   I   m not even sure exactly which version of RSX I   m looking for.   I think Phase-III was first released around 1980-81, but I   m not even sure of that.
  
Thanks,
Bob