1. R. Courant & K. O. Friedrichs, Supersonic Flow and Shock Waves, Wiley, 1948.
2. A. Gray, Tubes, Addison-Wesley, 1990.
3. W. Israel, Singular hypersurfaces and thin shells in general relativity, Il Nuovo Cimento, 54B. (1966), 1?14.
4. W. Israel, Dark stars: the evolution of an idea, in: 300 years of gravitation, edited by S. W. Hawking & W. Israel, Cambridge University Press, 1987, pp. 199?276.
5. P. D. Lax, Hyperbolic systems of conservation laws, II, Comm. Pure Appl. Math., 10 (1957), pp. 537?566.