1999, Alan Davies, Tradition and Modernity in Protestant Christianity, Karigoudar Ishwaran (editor), Ascetic Culture: Renunciation and Worldly Engagement, page 30
2004, Phyllis G. Jestice, Ascetics as Holy People, Phyllis G. Jestice (editor), Holy People of the World: A Cross-Cultural Encyclopedia, Volume 1: Entries A to G, page 70