Owing to the fact that a Living Reviews in Solar Physics article may evolve over time, we recommend to cite the article as follows:
P. F. Chen,
"Coronal Mass Ejections: Models and Their Observational Basis",
Living Rev. Solar Phys. 8, (2011), 1. URL (accessed <date>):
The date given as <date> then uniquely identifies the version of the article you are referring to.