The Gygax reference is a positive reference, I think.  Are you saying he should have said mid-to-late or late instead?  The dragon mag stuff is less positive.  How about just saying 1976 and getting rid of the mid?
It sounds like MA and Gamma World are kinda interchangeable in some people's minds.  Maybe that's what Schick meant?  How about "While D&D; is a fantasy roleplaying game, Expedition to the Barrier Peaks introduces science fiction elements into the game, and according to author Lawrence Schick, elements specifically from the Gamma World role-playing game." -   (contribs)