Mangel AW, Fehnel SE. End points in irritable bowel syndrome. Expert Rev Gastroenterol Hepatol. 2011 Jun 1;5(3):293-5.
Williams VSL, Wakeford ME. The predictive validity of the National Teacher Examinations for performance in teacher education programs. Educ Psychol Meas. 1993;53(2):533-9. doi: 10.1177/0013164493053002023