Owing to the fact that a Living Reviews in Relativity article may evolve over time, we recommend to cite the article as follows:
Peter Anninos,
"Physical and Relativistic Numerical Cosmology",
Living Rev. Relativity 1, (1998), 2. URL (accessed <date>):
http://www.livingreviews.org/lrr-1998-2
The date given as <date> then uniquely identifies the version of the article you are referring to.