1. On single and bimodal optimum buckling loads of clamped columns;Olhoff;Int. J. Solids Structures,1977
2. Singular solutions in structural optimization problems;Masur,1980
3. Singular dependence of repeated eigenvalues;Rousselet,1981
4. Optimization of structures with repeated eigenvalues;Choi,1981
5. Remarks on the optimal shape of the fixed-fixed column;Hu,1981