ETGEN, G. J. (1977). An Introduction to ordinary differential: Equations with difference equations, numerical methods and applications. Harper and Row.

ETGEN, Garret J. An Introduction to Ordinary Differential: Equations with Difference Equations, Numerical Methods and Applications. New York: Harper and Row, 1977.

ETGEN, Garret J. An Introduction to Ordinary Differential: Equations with Difference Equations, Numerical Methods and Applications. Harper and Row, 1977.