Owing to the fact that a Living Reviews in Relativity article may evolve over time, we recommend to cite the article as follows:
Abhay Ashtekar and Badri Krishnan,
"Isolated and Dynamical Horizons and Their Applications",
Living Rev. Relativity 7, (2004), 10. URL (accessed <date>):
The date given as <date> then uniquely identifies the version of the article you are referring to.