1. de Boer, R.: On plastic deformation of soils. Int. J. Plasticity4, 371?391 (1988).
2. de Borst, R.: Non-linear analysis of frictional materials. Ph. D. Diss., Teschnische Hogeschool Delft 1986.
3. Bronstein, I. N., Semendjajew, K. A.: Taschenbuch der Mathematik. Zürich Frankfurt/M.: Harri Deutsch 1971.
4. Chen, W. F., Saleeb, A. F.: Constitutive equations for engineering materials. New York: Wiley-Interscience 1982.
5. Chen, W. F., Mizuno, E.: Nonlinear analysis in soil mechanics. In: Developments in geotechnical engineering 53. New York: Elsevier 1990.