Owing to the fact that a Living Reviews in Relativity article may evolve over time, we recommend to cite the article as follows:
J. Fernando Barbero G. and Eduardo J. S. Villaseñor,
"Quantization of Midisuperspace Models",
Living Rev. Relativity 13, (2010), 6. URL (accessed <date>):
The date given as <date> then uniquely identifies the version of the article you are referring to.