Enter a clue or pattern or both:
The Clue
Multivolume ref., usually (5 letter answer)
The Answer
ENCYC
Tags
Notes
The answer ENCYC is rarely seen, appearing only about once every 1800 puzzles.
Related Clues
Britannica, for one: Abbr.
Multivolume ref.
Ref. work
Reference bk.
Reference vol.
Atlas shelfmate: Abbr.
It comes in volumes: Abbr.