Owing to the fact that a Living Reviews in Solar Physics article may evolve over time, we recommend to cite the article as follows:
Ilya G. Usoskin,
"A History of Solar Activity over Millennia",
Living Rev. Solar Phys. 5, (2008), 3. URL (accessed <date>):
The date given as <date> then uniquely identifies the version of the article you are referring to.