Owing to the fact that a Living Reviews in Relativity article may evolve over time, we recommend to cite the article as follows:
Piotr T. Chruściel and João Lopes Costa and Markus Heusler,
"Stationary Black Holes: Uniqueness and Beyond",
Living Rev. Relativity 15, (2012), 7. URL (accessed <date>):
The date given as <date> then uniquely identifies the version of the article you are referring to.