Gray literature is literature that is scholarly, but not peer-reviewed nor published in a "traditional" scholarly format such as a university press book or a scientific journal.

Examples of gray literature are:

• Posters
• Conference Proceedings
• Government Reports/Webpages/Statistics
• Reputable Nonprofit Organization Reports/Webpages/Statistics
• Interactive Maps
• Datasets or Databases 
• Preprints (articles that are posted to a preprint server before they are submitted to a journal and PRIOR to being peer reviewed)
• Working papers
• Academic dissertations and theses

Gray literature can help inform our search strategy. We can also learn from gray literature what research is currently being, as many scholars don't publish all of their work in an peer-reviewed paper until their findings are complete. We also need to recognize that not all researchers work in academia; many of them work in the corporate, nonprofit, or government sectors. By reading and understanding how research is being currently done in the field, we can get a fuller picture of our research topic(s).

A lot of grey literature can be found on the open web (the publicly accessible web that you are using when you "Google" something, as opposed to the limited access web that includes things like the databases that the library pays for). However, that does not necessarily mean that it is easy to find. 

• Advanced Google Search
  • Use operators to narrow results for complex searches
• Perplexity.ai always consult your instructor before using any AI tool for a course assignment
  • Perplexity is an AI search engine that uses retrieval augmented generation to search the web for sources to answer your question. Free accounts have a limited number of Deep Research queries. Toggle from the "answer" page to the "sources page"

Note that AI search engines are not appropriate for systematic reviews because the searches cannot be replicated.