Wikipedia:Tip of the day/September 18, 2006

Cite your sources

Wikipedia articles should focus on describing facts in a neutral fashion. When writing about facts, cite sources that can verify the information being presented. Stick to a factual style even when writing about fiction or opinions. Providing references is particularly important for controversial opinions - instead of using weasel words like some people believe... you should cite sources to help readers know who believes what, and why.