Owing to the fact that a Living Reviews in Relativity article may evolve over time, we recommend to cite the article as follows:
Jean-Yves Vinet,
"On Special Optical Modes and Thermal Issues in Advanced Gravitational Wave Interferometric Detectors",
Living Rev. Relativity 12, (2009), 5. URL (accessed <date>):
http://www.livingreviews.org/lrr-2009-5
The date given as <date> then uniquely identifies the version of the article you are referring to.