Karen Kingston (2016). “Clear Your Clutter with Feng Shui (Revised and Updated): Free Yourself from Physical, Mental, Emotional, and Spiritual Clutter Forever”, p.189, Harmony
Cecilia Payne-Gaposchkin, Katherine Haramundanis (1996). “Cecilia Payne-Gaposchkin: An Autobiography and Other Recollections”, p.85, Cambridge University Press