(en) Barbara E Bryden, Sundial : Theoretical Relationships Between Psychological Type, Talent, And Disease, Gainesville, Floride, Center for Applications of Psychological Type, , 327 p. (ISBN978-0-935652-46-8 et 0-935652-46-9, lire en ligne).
(en) Greg Roza, An Optical Artist : Exploring Patterns and Symmetry, Rosen Classroom, , 32 p. (ISBN978-1-4042-5117-5, lire en ligne), p. 20.