Ah, grey literature! Confronted with a vast void of faceless, nameless literature, it’s easy to quickly become overwhelmed. Where do I start? What do I search? What am I even looking for?
As a medical librarian, I’m used to structured searches in curated databases, and going into the unknown can be a frightening thought. However, it is possible to add structure to a grey literature search!
First: What are you looking for?
Too often, the idea of “grey literature” is lumped into one monolithic term. In reality, grey literature is a broad umbrella term and encompasses a lot of different document types whose main commonality is that they are unpublished or published outside traditional publishers: basically, anything that’s not a traditional published research article.
Think about the research project at hand and what types of literature would best support it. For example, in a qualitative synthesis or realist review of a social sciences topic, a lot of robust evidence might come from book chapters with unpublished studies. In a mapping review in health services research, government white papers/reports about local health initiatives might be most relevant. What do you expect the evidence to look like, and where might you go about finding it?
- Reports or white papers
- Theses and dissertations
- Book chapters
- Clinical trials registers
- Conference proceedings
Second: Make a plan!
Next, make a detailed plan for searching the literature. Your searching plan should contain information about what sources will be searched, how they will be searched, how the searches will be documented, and how/where the potentially relevant documents will be downloaded/stored.
Some strategies to consider including in your plan might be:
- Traditional database searches that will include grey lit such as conference abstracts (e.g. PyscINFO, Embase, Proquest Theses and Dissertations)
- Specialised databases (e.g. “grey” databases such as OpenGrey or HMIC, or small subject-specific databases without sophistocated search mechanisms)
- Search engines (e.g. Google, GoogleScholar, DuckDuckGo)
- Custom Google search engines (e.g. NGOs search, Just State Web Sites; Think Tank Search)
- Clinical Trials registers
- Hand searching of key subject websites (e.g. the main associations or government departments in that topic area)
- Consultation with experts (who may have ideas about papers you have missed)
For each strategy, document all the details you will need to conduct the search:
- Who is going to conduct the search?
- What search terms or search strategies will be used?
For more sophistocated sites, a full boolean strategy might be used, but for a site with a simple search box, perhaps one term or a few terms at a time might need to be used. Strategies should be similar, but adapted for the searching capabilities of that resource.
Think also about the context: if your search topic is “yoga for substance abuse”, and you’re searching the NIDA International Drug Abuse Research Abstract Database, you won’t need to include substance abuse terminology in your searches, because everything in that subject database is already about substance abuse.
- How will the searches be documented? Oftentimes, an excel spreadsheet will suffice with information such as the person searching, the date, the searching strategy, number of items looked at, and the number of items selected as potentially relevant. Bear in mind that for some resources, the searching strategy might be narrative, such as “clicked the research tab and browsed the list of publications”.
- How many results will you look at? The first 50? The first 100? Until there are diminishing returns?
Third: Execute the plan!
Make sure to have a strategy in place for recording your searches and downloading your citations. Due to the transient nature of the web, grey literature searches generally aren’t replicable. When you search google one week, and conduct the same search a year later, you might get different results. However, searches for grey literature can and should be transparent and well-documented, such that someone else could conduct the same searches at a later point, even if they would get different results.
For more information, check out the following:
Briscoe S. Web searching for systematic reviews: a case study of reporting standards in the UK Health Technology Assessment programme. BMC research notes. 2015 Apr 16;8(1):153.
Godin K, Stapleton J, Kirkpatrick SI, Hanning RM, Leatherdale ST. Applying systematic review search methods to the grey literature: a case study examining guidelines for school-based breakfast programs in Canada. Systematic reviews. 2015 Oct 22;4(1):138.
For a helpful list of grey literature sources to include in your search, also check out the Grey Matters tool published by the research information specialist team at CADTH.