Sumber : • Fauci, Braunwald, Kasper et al. "Harrison’s Manual of Medicine 17th Edition". USA: The Mc-Graw Hill Companies; 2009 • Dewanto G, Suwono WJ, Riyanto B, Turana Y. "Panduan Praktis: Diagnosis & Tata Laksana Penyakit Saraf". Jakarta : EGC; 2009 • http://www/. aafp.org/ • http://www.webmd.com/ • http://emedicine.medscape.com/