[1] J. L. Lions, Optimal Control of Systems Governed by Partial
Differential Equations, Springer-Verlag, Band, 170 (1971).
[2] H. O. Fattorini, The Time Optimal Problem for Distributed Control
of Systems Described by the Wave Equation, In: Aziz, A. K.; Wingate,
J. W.; Balas, M. J. (eds.): Control Theory of Systems Governed by
Partial Differential Equations, Academic Press, New York, San
Francisco, London, 1957.
[3] W. Krabs, On time-minimal distributed control of vibrating systems
governed by an abstract wave equation, Appl. Math. Optim. 13 (1985),
137-149.
[4] H. A. El-Saify, H. M. Serag and M. A. Shehata, Time-optimal
control for co-operative hyperbolic systems involving Laplace
operator, Journal of Dynamical and Control Systems 15(3) (2009),
405-423.
[5] R. A. Adams, Sobolev Spaces, Academic Press, New York, 1975.
[6] J. Fleckinger, J. Hernández and F. D. E. Thélin, On the
existence of multiple principal eigenvalues for some indefinite linear
eigenvalue problems, Rev. R. Acad. Cien. Serie A. Mat. 97(2) (2003),
461-466.
[7] J. L. Lions and E. Magenes, Non homogeneous boundary value problem
and applications, Springer-Verlag, New York, I, II, 1972.
[8] J. L. Lions, Remarks on approximate controllability, J. Anal.
Math. 59 (1992), 103-116.
[9] Enrique Zuazua, Controllability of partial differential equations
and its semi-discrete approximations, Discrete and Continuous
Dynamical Systems 8(2) (2002), 469-513.
[10] H. O. Fattorini, Time-optimal control of solutions of operational
differential equations, SIAM Journal on Control 3 (1964), 54-59.
[11] H. O. Fattorini, Ordinary differential equations in linear
topological spaces, II, Jour. Diff. Equations 6 (1969), 50-70.
[12] H. Tanabe, On differentiability and analyticity of weighted
elliptic boundary-value problems, Math. J. Osaka 2(2) (1965), 163-190.