deCarvalho, Roy J. (1999). "Otto Rank, the Rankian Circle in Philadelphia, and the Origins of Carl Rogers' Person-Centered Psychotherapy". History of Psychology. 2 (2): 132–148. doi:10.1037/1093-4510.2.2.132. PMID11623737.
deCarvalho, Roy J. (1999). "Otto Rank, the Rankian Circle in Philadelphia, and the Origins of Carl Rogers' Person-Centered Psychotherapy". History of Psychology. 2 (2): 132–148. doi:10.1037/1093-4510.2.2.132. PMID11623737.