1. Attiyeh, G. (1999). Determinants of persistence of graduate students in Ph.D. programs. Princeton: Educational Testing Service.
2. Baird, L. L. (1993). Using research and theoretical models of graduate student progress. In L. L. Baird (Ed.), Increasing graduate student retention and degree attainment (pp. 3–12). San Francisco: Jossey-Bass.
3. Berelson, B. (1960). Graduate education in the United States. New York: McGraw-Hill.
4. Berg, H. M., & Ferber, M. A. (1983). Men and women graduate students: who succeeds and why? The Journal of Higher Education, 54(6), 629–648. doi: 10.2307/1981934 .
5. Biglan, A. (1973). The characteristics of subject matter in different academic areas. The Journal of Applied Psychology, 57, 195–203. doi: 10.1037/h0034701 .