Murder By Mail: Inside the mystery book clubs - with complete checklist, Michael L. Cook. Bowling Green, Ohio : Bowling Green University Popular Press, 1983.

The Armchair Detective, Volume 8, by Allen J. Hubin, Taylor & Francis, August 1, 1986.

Zane Grey's West Society, The Writings of Zane Grey, Walter J. Black Editions 

The Classics Club, Walter J. Black Editions