1. B.D.O. Anderson and J.B. Moore, ?Optimal control: Linear-Quadratic methods?, Prentice-Hall, Englewood Cliffs, (1989).
2. S.P. Banks, ?State-space and frequency-domain methods in the control of distributed parameter systems?, Peter Peregrinus, Londonvol. 3 (1983).
3. F.M. Callier ?Partially stable LQ-optimal control by spectral factorization, International Journal of Control, vol.39, no. 3, pp. 523?539, (1984).
4. F.M. Callier, ?Recent advances on spectral factorization and LQ-optimal regulation for multivariable distributed systems?, Proceedings of the International Symposium MTNS-91, Kobe, Japan, pp.83?91, (1991).
5. F.M. Callier and C.A. Desoer, ?An algebra of transfer functions for distributed linear time-invariant systems?, IEEE Transactions on Circuits and Systems,vol. CAS-25, no. 9, pp. 651?662, (1978); correction, ibid. IEEE Transactions on Circuits and Systems,vol. 26, p. 360, (1979)).