Grey literature is often publicly available and is rarely peer-reviewed in the way that high-quality scholarly literature is. It is therefore important to evaluate the grey literature you find, to make sure it is of high quality.
There are various tools and checklists you can use to do this, try one of these:
Alternatively use the All Ws method to ask:
If the answer to most of these questions is ‘no’, we advise you not to trust it as a source unless you find information to back it up in more credible sources such as peer-reviewed articles. If you are not sure about whether the source you have found can be considered trustworthy, feel free to get in touch.