David Wolfe (2013). “Longevity Now: A Comprehensive Approach to Healthy Hormones, Detoxification, Super Immunity, Reversing Calcification, and Total Rejuvenation”, p.20, North Atlantic Books
Rivka Horwitz, Martin Buber (1988). “Buber's way to "I and thou": the development of Martin Buber's thought and his "Religion as presence" lectures”, Jewish Pubn Society