Barrabes, C., & Hogan, P. A. (2003). Singular null hypersurfaces in general relativity: Light-like signals from violent astrophysical events. World Scientific.

Barrabes, Claude, and P. A. Hogan. Singular Null Hypersurfaces in General Relativity: Light-like Signals from Violent Astrophysical Events. River Edge, N.J.: World Scientific, 2003.

Barrabes, Claude, and P. A. Hogan. Singular Null Hypersurfaces in General Relativity: Light-like Signals from Violent Astrophysical Events. World Scientific, 2003.