1. V. A. Yakubovich, ?Solution of certain matrix inequalities appearing in control theory,? Dokl. Akad. Nauk SSSR,143, No. 3, 1304?1307 (1962).
2. R. E. Kalman, ?Lyapunov functions for the problem of Lur'e in automatic control,? Proc. Nat. Acad. Sci. USA,49, No. 2, 201?205 (1963).
3. F. R. Gantmakher and V. A. Yakubovich, ?Absolute stability of nonlinear controlled systems,? in: Proc. of the Second All-Union Congr. on Theoretical and Applied Mechanics [in Russian], Nauka, Moscow (1965).
4. V. M. Popov, Hyperstability of Control Systems [in Russian], Nauka, Moscow (1970).
5. K. R. Meyer, ?Lyapunov functions for the problems of Lur'e,? Proc. Nat. Acad. Sci. USA,53, No. 3, 501?503 (1965).