Tolong jelaskan mengenai Bacaan tambahan dari Perkumpulan rahasia

Harwood, W. S. "Secret Societies in America," The North American Review, Vol. 164, No. 486, May, 1897.

Stephen Klimczuk, Gerald Warner (2009). Secret Places, Hidden Sanctuaries: Uncovering Mysterious Sights, Symbols, and Societies, New York: Sterling Publishing Company.