Citing this Article
 

Owing to the fact that a Living Reviews article may evolve over time, we recommend to cite the article as follows:

Jeffrey Winicour ,
"Characteristic Evolution and Matching",
Living Rev. Relativity 12,  (2009),  3. URL (cited on <date>):
http://www.livingreviews.org/lrr-2009-3

The date given as <date> then uniquely identifies the version of the article
you are referring to.