Amateur Press Association.
Of potential interest:
The Loyal Opposition. A "symposium" zine arguing about Breen, published by John and Bjo Trimble in March 1964. Contributors: Al Lewis, Dick Ellington, Bob Lichtman, Bill Donaho, Don Fitch, John Boardman, Marion Zimmer Bradley, Walter Breen, Ray Nelson.
The Report (from the Pacificon committee)
Starspinkle #35