1.

R. D. James, The propagation of phase boundaries in elastic bars, *Arch. Rational Mech. Anal.*
**73** (1980) 125–158.

2.

M. Shearer, Riemann problem for a class of conservation laws of mixed type, *J. Diff. Eqs.*
**46** (1982) 426–443.

3.

M. Shearer, Nonuniqueness of admissible solutions of Riemann initial value problems for a system of conservation laws of mixed type, *Arch. Rational Mech. Anal.*
**93** (1986) 45–59.

4.

M. Shearer, Dynamic phase transitions in a van der Waals gas, *Quart. Appl. Math.*, **46** (1988) 631–636.

5.

L. Hsiao, Admissibility criterion and admissible weak solutions of Riemann problem for conservation laws of mixed type, Workshop Proceedings on Nonlinear Evolution Equations that Change Type, to appear in *IMA Volumes in Mathematics and its Applications*.

6.

J. Glimm, The interactions of nonlinear hyperbolic waves, *Comm. Pure Appl. Math.*
**41** (1988) 569–590.

7.

M. Slemrod, A limiting “viscosity” approach to the Riemann problem for materials exhibiting change of phase, *Arch. Rational Mech. Anal.*
**105** (1989) 327–365.

8.

A. S. Kalašnikov, construction of generalized solutions of quasi-linear equations of first order without convexity conditions as limits of solutions of parabolic equations with a small parameter, *Dokl. Akad. Nauk. SSSR*
**127** (1959) 27–30.

9.

V. A. Tupčiev, The asymptotic behavior of the solutions of Cauchy problem for the equation *ɛ*
^{2}
*tu*
_{xx}=u_{t}+[φ(u)]_{x}that degenerates for *ξ*=0 into the problem of the decay of an arbitrary discontinuity for the case of a rarefaction wave, *Z. Vyčisl. Mat. Fis.*
**12** (1972) 770–775; English translation in *USSR Comput. Math. Phys.*
**12**.

10.

V. A. Tupčiev, On the method of introducing viscosity in the study of problems involving the decay of discontinuity, *Dokl. Akad. Nauk. SSSR*
**211** (1973) 55–58.

11.

C. M. Dafermos, Solutions of the Riemann problem for a class of hyperbolic conservation laws by the viscosity method, *Arch. Rational Mech. Anal.*
**52** (1973) 1–9.

12.

C. M. Dafermos, Structure of the solutions of the Riemann problem for hyperbolic conservation laws, *Arch. Rational Mech. Anal.*
**53** (1974) 203–217.

13.

C. M. Dafermos, Admissible wave fans in nonlinear hyperbolic system, *Arch. Rational Mech. Anal.*
**106** (1989) 243–260.

14.

C. M. Dafermos & R. J. DiPerna, The Riemann problem for certain classes of hyperbolic systems of conservation laws, *J. Diff. Eqs.*
**20** (1976) 90–114.

15.

M. Slemrod & A. Tzavaras, A limiting viscosity approach for the Riemann problem in isentropic gas dynamics, *Indiana Univ. Math. J.*
**38** 1989 1047–1074.

16.

Haitao Fan, The structure of the solutions of the gas dynamics equation and the formation of the vacuum state, submitted to *Quart. Appl. Math.*