<P> Wikipedia: Verifiability is an important and core policy of Wikipedia . Article content should be backed up by reliable sources wherever needed to show that the presentation of material on Wikipedia is consistent with the views that are presented in scholarly discourse or the world at large . Such sources help to improve the encyclopedia . </P> <P> However, many editors misunderstand the citation policy, seeing it as a tool to enforce, reinforce, or cast doubt upon a particular point of view in a content dispute, rather than as a means to verify Wikipedia's information . This can lead to several mild forms of disruptive editing which are better avoided . Ideally, common sense would always be applied but Wiki - history shows this is unrealistic . Therefore, this essay gives some practical advice . </P> <P> Not citing common knowledge and not providing bibliographic entries for very famous works is also consistent with the major academic style guides, such as The MLA Style Manual and the APA style guide . </P> <P> Sometimes editors will insist on citations for material simply because they dislike it or prefer some other material, not because the material in any way needs verification . For example, an editor may demand a citation for the fact that most people have five digits on each hand (yes, this really happened). Another may decide that the color of the sky is actually aqua rather than blue, pull out an assortment of verifiable spectrographic analyses and color charts to demonstrate that this position is actually correct, and follow that with a demand that other editors provide equivalent reliable sources for the original statement that the sky is in fact blue . While there are cases where this kind of pedantic insistence is useful and necessary, often it is simply disruptive, and can be countered simply by pointing out that there is no need to verify statements that are patently obvious . If the alternate proposition merits inclusion in the article under other policies and guidelines it should of course be included, but it should in no way be given greater prominence because it is sourced . </P>

When don't you need to cite a source