1. V. M. Babich,The Hadamard Ansatz, its analogies, generalizations and applications. St. Petersburg Math. J.,3, no. 5, 937?972 (1992).
2. B. D. Coleman, M. Fabrizio and D. R. Owen,On the thermodynamics of second sound in dielectric crystals. Arch. Rational Mech. Anal,80, no. 2, 135?158 (1982).
3. R. Courant,Partial Differential Equations. Interscience Publ. Div. of John Wiley & Sons, New York/London 1962.
4. H. O. Fattorini,The hyperbolic singular perturbation problem: An operator theoretic approach, J. Diff. Equal.,70, 1?41 (1987).
5. I. M. Gelfand and E. S. Shilov,The Generalized Functions, Vol. 1. Academic Press, London 1964.