1. R. P. Agnew, Differential Equations, McGraw-Hill, New York, 1942.
2. R. G. D. Allen, Mathematical Economics, 2nd ed., Macmillan, London, 1965.
3. Arthur Benavie, Mathematical Techniques for Economic Analysis, Prentice-Hall, Englewood Cliffs, NJ, 1972.
4. Alpha C. Chiang, Fundamental Methods of Mathematical Economics, 2nd ed., McGraw-Hill, New York, 1974, Chapter 12.
5. Jean E. Draper and Jane S. Klingman, Mathematical Analysis, 2nd ed., Harper and Row, New York, 1972, Chapter 3.