Schrag, A. F., Poland, R. P., & Popham, E. L. (1987). A system for teaching business education (2nd ed.). Gregg Division, McGraw-Hill.
Cita Chicago (17th ed.)Schrag, Adele Frisbie, Robert P. Poland, i Estelle L. Popham. A System for Teaching Business Education. 2nd ed. New York: Gregg Division, McGraw-Hill, 1987.
Cita MLA (9th ed.)Schrag, Adele Frisbie, et al. A System for Teaching Business Education. 2nd ed. Gregg Division, McGraw-Hill, 1987.
Atenció: Aquestes cites poden no estar 100% correctes.