1. Fox, C. (1987). An introduction to the calculus of variations. New York: Dover Publications, Inc.
2. Lanczos, C. (1986). The variational principles of mechanics. New York: Dover Publications, Inc.
3. Cook, R. D., Malkus, D. S., & Plesha, M. E. (1989). Concepts and applications of finite element analysis. New York: Wiley.
4. Shames, I. H., & Dym, C. L. (2003). Energy and finite element method in structural mechanics. New York: Taylor & Francis.
5. Pedersen, P., & Seyranian, A. P. (1983). Sensitivity analysis for problems of dynamic stability. International Journal of Solids and Structures, 19, 315–335.