1. Stability by Liapunov's Direct Method with Applications;LaSalle,1961
2. Stability of Non-Linear Systems of Automatic Control;Bedel'baev,1960
3. The formula of Liapounoff function of system of linear differential equations with constant coefficients;Tsai;Acta Math. Sinica,1959
4. Über die Anwendung der Methode von Ljapunov auf Differenzen-gleichungen;Hahn;Math. Ann.,1958
5. Operational Methods for Linear Systems;Kaplan,1962