1. A.V. Balakrishnan, "Optimal control problems in Banach spaces", J.S.I.A.M. Control, 1965, pp. 152–179.
2. A.V. Balakrishnan, "Boundary control of parabolic equations: L-Q-R theory", Proc. Conf. on theory of Nonlinear Equations, Sept. 1977, Akademic Verlag, Berlin 1978.
3. R.F. Curtain and A.J. Pritchard, "An abstract theory for unbounded control action for distributed parameter systems", S.I.A.M. J. Control and Optim. 15 (1977) pp. 566–611.
4. R.F. Curtain and A.J. Pritchard, "Infinite dimensional linear systems theory". Lecture Notes in Control and Information Sciences, Vol. 8, Springer Verlag, 1978.
5. R.F. Curtain, "Finite dimensional compensators for parabolic distributed systems with unbounded control and observation (to appear in S.I.A.M. J. Control and Optimization).