1. R. Bellman, Stability theory for nonlinear ordinary differential equations.
2. M.R. Li, Estimates for the life-span of solutions for semilinear wave equations, Proceedings of the Workshop on Differential Equations V, January 10–11, 1997, National Tsing-Hua University, Hsinchu, Taiwan, pp. 129–138.
3. On the semilinear wave equations;Li;Taiwanese J. Math.,1998
4. M.R. Li, Estimates for the life-span of positive solutions of some semilinear wave equations in 2-dimensional bounded domains □u=up, Proceedings of the Workshop on Differential Equations VII, May 1999, National Chung-Hsing University, Taichung, Taiwan, pp. 119–134.
5. M.R. Li, Estimates for the life-span of solutions of semilinear wave equations, preprint.