1. Finite elements based on energy orthogonal functions
2. Finite elements with increased freedom in choosing shape functions
3. ‘The free formulation for nonlinear finite elements with application to shells’, Dr. ing. Thesis, Division of Structural Mechanics, The Norwegian Institute of Technology, Trondheim, 1986 34.
4. and , ‘Nonlinear shell analysis using free formulation finite elements’, in et al. (eds.), Finite Element Methods for Nonlinear Problems, Springer-Verlag, Berlin, 1985.
5. The Finite Element Method, 3rd edn, McGraw-Hill, London, 1977.