1. W. Hayes, inFundamentals of Gas Dynamics, edited by H. Emmons (Princeton University Press, Princeton, New Jersey, 1958), Vol. 3, p. 451.
2. The lines ψ = const and t = const are thecharacteristicsof Eqs. (1). For example, see P. A. Lagerstrom, J. D. Cole, and L. Trilling,Problems in the Theory of Viscous Compressible Fluids(California Institute of Technology, Pasadena, California, 1949), p. 19.
3. G. Birkhoff,Hydrodynamics(Princeton University Press, Princeton, New Jersey, 1960), p. 116.
4. These results should be compared with the self-symmetric solutions for polytropic processes (See reference 1).