Brauer, F., & Nohel, J. A. (1969). The qualitative theory of ordinary differential equations: An introduction. W.A. Benjamin.

Brauer, Fred, and John A. Nohel. The Qualitative Theory of Ordinary Differential Equations: An Introduction. New York: W.A. Benjamin, 1969.

Brauer, Fred, and John A. Nohel. The Qualitative Theory of Ordinary Differential Equations: An Introduction. W.A. Benjamin, 1969.