1. Stability Theory of Differential Equations;Bellman,1953
2. Asymptotic Behavior and Stability Problems in Ordinary Differential Equations;Cesari,1963
3. Stability and Asymptotic Behavior of Differential Equations;Coppel,1965
4. Disconjugacy;Coppel,1971
5. On the Laplace-Fourier transcendents;Hartman;Amer. J. Math.,1949