Here you can extensively browse in old computer magazines. In particular, U.S. journals are expected for users on this side of the pond be interesting (and perhaps some "pearl" included.)
After probably most used CP/M command "PIP" the CFOG usergroup named their monthly newspaper. As more and more CP/M related articles were replaced by contributing articles about IBM XT and MS-DOS the name of "Chicago's First Osborne Group" was changed in "Chicago's Finest User Group", the abbreviation CFOG but was retained.
Articles and information about the Z-system from the "Morrow Owner's Review" (MOR).
Articles and information about the Z-system from the "The Computer Journal" (TCJ).