1. Y. M. Tsai and H. Kolsky, J. Mech. Phys. Solids, 15 (1967) 29.
2. H. Hertz, Leipzig Barth, 1 (1882) 174.
3. A. E. H. Love, A Treatise on the Mathematical Theory of Elasticity, Cambridge University Press, 193 (1927).
4. Y. M. Tsai, Stress Distribution in Elastic and Visco-elastic Plates Subjected to Symmetrical Rigid Indentations, ERI-171 Preprint, Engineering Research Institute, Iowa State University, 1968 (to appear in Quar. Appl. Math.).
5. Y. M. Tsai and H. Kolsky, J. Mech. Phys. Solids, 15 (1967) 263.