Citing this Article
 

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

Sean M. Carroll ,
"The Cosmological Constant",
Living Rev. Relativity 3,  (2001),  1. URL (cited on <date>):
http://www.livingreviews.org/lrr-2001-1

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