H.G. Kippenberg and G.G. Stroumsa, Secrecy and Concealment: Studies in the History of Mediterranean and Near Eastern Religions, (Leiden 1995)

Harvey J. Hames, Exotericism and Esotericism in Thirteenth Century Kabbalah

Ben Gurion University

http://www.esoteric.msu.edu/VolumeVI/KabbalahHames.htm