In this paper, a unique classical solution (v, u) of the Cauchy proble
m (1), (2) is obtained if \v(0)(x)\(1+alpha) less than or equal to M,
\u(0)(x)\(2+alpha) less than or equal to M. The a priori estimates \v(
x, t)\(1+alpha), \u(x, t)\(2+alpha) less than or equal to M(T) are obt
ained by using the maximum principle without the restriction lim(\x\--
>+/-infinity) (v(0)(x), u(0)(x)) = (v(+/-), u(+/-)), where v(+/-), u(/-) are constants. This resolves a problem proposed by J. A. Smeller (
''Shock Waves and Reaction-Diffusion Equations,'' p. 444, Springer-Ver
lag, New York/Berlin, 1982) for The viscoelastic system. A parallel re
sult (Theorem 8) for a model (42) of compressible adiabatic flow throu
gh porous media with a physical viscosity is also obtained. (C) 1998 A
cademic Press.