Ross, S. L., & Ross, S. L. (1989). Introduction to ordinary differential equations (4th ed.). Wiley.

Ross, Shepley L., and Shepley L. Ross. Introduction to Ordinary Differential Equations. 4th ed. New York: Wiley, 1989.

Ross, Shepley L., and Shepley L. Ross. Introduction to Ordinary Differential Equations. 4th ed. Wiley, 1989.