William Oster, The Principles and Practice of Medicine: Designed for the Use of Practitioners and Students of Medicine (1928?), Chapter IV, Tuberculosis, p.306 [google books]
Plato 380 B.C. Plato (2006) [380 BC], Protagoras, Internet Classics Archive: The University of Adelaide Library, consultado em 17 de dezembro de 2006
Plato 360 B.C. 270c Plato (2012) [360 BC], Phaedrus, Internet Classics Archive: The University of Adelaide Library, consultado em 1 de novembro de 2012