Grey literature is something that has not been published for commercial purposes or outside of tradition publishing channels. It is often produced by individuals or organisations.
Grey literature can include:
Some information isn't published formally anywhere else and is only available as grey literature. It can be representative of specific locales or settings e.g. local NHS trust information, community newsletters. It can provide personal stories. It can also be an excellent source of data.
However, because grey literature isn't peer reviewed, it should be used with caution and the awareness that it could be biased, be based on opinion, or contain false/incorrect information.
Grey literature can sometimes be difficult to find, but there are a number of resources available to help. Below is a list of different types of grey resources, including theses respositories/search engines, broader grey-specific search sites, and some health grey literature resources. You may find additional grey literature on charity websites.
The format of your reference will vary according to the type of literature you are citing.
Leaflets and pamphlets can be cited using this reference builder on the referencing website.
Other documents, like posters or financial reports have their own section of the referencing guide, so check which format has the closest match to the item you are citing.