The following references provide additional information on nonlinear finite element methods. They allow the interested user to explore the topic in more depth.
General texts on nonlinear analysis
Belytschko, T., W. K. Liu, and B. Moran, Nonlinear Finite Elements for Continua and Structures, Wiley & Sons, 2000.
Bonet, J., and R. D. Wood, Nonlinear Continuum Mechanics for Finite Element Analysis, Cambridge, 1997.
Cook, R. D., D. S. Malkus, and M. E. Plesha, Concepts and Applications of Finite Element Analysis, Wiley & Sons, 1989.
Crisfield, M. A., Non-linear Finite Element Analysis of Solids and Structures, Volume I: Essentials, Wiley & Sons, 1991.
Crisfield, M. A., Non-linear Finite Element Analysis of Solids and Structures, Volume II: Advanced Topics, Wiley & Sons, 1997.
E. Hinton (editor), NAFEMS Introduction to Nonlinear Finite Element Analysis, NAFEMS Ltd., 1992.
Oden, J. T., Finite Elements of Nonlinear Continua, McGraw-Hill, 1972.