1. Problèm Générale de la Stabilité de Mouvement;Liapounoff,1949
2. Stability of Motion;Hahn,1967
3. Stability Theory by Liapunov’s Direct Method;Rouche,1977
4. On a theorem on stability;Marachkov;Bull. Soc. Phys.-Math. Kazan,1940
5. Stability theory for ordinary differential equations;LaSalle;J. diff. Eqns.,1968