Schutz, Bernard F. Astrophysical Relativity, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;
schutz_60525.pdf (Publisher version), 2MB
Schutz, B. F., & Comins, N. (1978). On the ergoregion instability. Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, 364(1717), 211-266. doi:10.1098/rspa.1978.0196.