Rugh 1994. Rugh, Svend E. (1994). "Chaos in the Einstein Equations -- characterization and importance?". Deterministic Chaos in General Relativity. Kananaskis, Alberta, Canada: Springer Science+Business Media New York. pp. 359–422. doi:10.1007/978-1-4757-9993-4. ISBN978-1-4757-9995-8.