Wikipedia articles operate on an assumption of "Verifiability" where every statement in an article should be "verifiable" in a footnoted source, preferably a source that is OA. By checking a footnote to a reliable source in any Wikipedia article, you help Wikipedia readers worldwide.
When adding a citation to the article, please include the hashtag #OAWiki in the edit summary so that we can track participation.
What makes a source good to add as an OA reference in Wikipedia?
Published: and peer-reviewed if possible.
Available: can readers access the source?
Reliable: it's a source you'd point a patron to if they wanted to know more.
Secondary: secondary sources are better to cite than primary material, except in cases of specific facts, like official census figures.
Actually supports the text: the source should back up what is stated. If it doesn't, but is a good general resource for the topic (such as a specialty encyclopedia), consider adding the source to a "further reading" section.
Pro tip: If you make a good effort at finding an OA source to confirm the statement on Wikipedia, but can't find one, leave the source as is. Wikipedia's principles around sourcing and Verifiability require that every statement that is controversial be supported by a reference or be removed if it's likely untrue.
Find an article with sourcing problems
There is lots of great research that is available OA but that is not cited in Wikipedia articles. Part of our goal is to locate this research.
If you are interested in working on articles from a particular topic area on English Wikipedia, there is an index of work for those topic areas. Here is how to use it:
Another strategy for finding a Wikipedia article to work on is simply browsing Wikipedia or using it for your own research. Every article on Wikipedia needs more sources, so either add new footnotes to verify content, or if there is a relevant source that doesn't link to a specific fact feel free to add sources to the "Further reading" sections. Once you have found an article, follow the instructions here for adding a reference.