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Scoping reviews

About Grey Literature?

The term grey literature is used to describe a wide range of different information that is produced outside of traditional publishing and distribution channels, and which is often not well represented in indexing databases.

A widely accepted definition in the scholarly community for grey literature is

"information produced on all levels of government, academia, business and industry in electronic and print formats not controlled by commercial publishing" ie. where publishing is not the primary activity of the producing body." 

From: Third International Conference on Grey Literature in 1997 (ICGL Luxembourg definition, 1997  - Expanded in New York, 2004).

Types of Grey Literature

News sources can be invaluable research resources. 

There are various types of news sources you can choose from, including:

  • newspapers
  • newsreels
  • newswires
  • news magazines
  • news monitoring services etc. 

Although, not always considered as grey literature sources in all subject areas, the news sources can be helpful in assisting in the discovery of grey literature.  For example, news items may flag the latest research report or findings, record speeches, contain statistics and other data not otherwise published.

There is a huge amount of news research material available to you at the University. Use the News Sources guide to find out more and access the news sources. 

News Sources LibGuide

Official publications can be broadly defined as the documents and materials produced by the government and governmental departments during the course of government business.

Content ranges from statements of law and policy to government reports and statistics.  These publications can be a valuable primary research source and are especially useful to those researching in law, politics and history.  However, they are of relevance across all subjects as they address all aspects of governmental work such as science, education, law, agriculture, transport, health etc.

To find out more about finding and using official publications, take a look at the Official Publications LibGuide

View the list of Official Publications databases in the Database A-Z List

A useful list of Country URLs is maintained by the UN E-Government Knowledgbase which gives quick access to the national government website portals from around the world.

A thesis or dissertation is a document submitted in support of candidature for a higher degree or professional qualification, presenting the author’s research and findings. Theses are extremely valuable sources of information, as they consist of substantial primary research in specialised topics and provide very detailed data and analysis.

They will also have extensive bibliographies, detailing the published literature on the given research topic.

Use the Finding Theses Quick Guide to learn more about tracking down theses in your field of study both at the University of Exeter and elsewhere. 

You can access dissertation and theses databases via the Database A-Z. The recommended databases for global dissertation searching is:

Clinical trial registries are helpful for locating trials that haven't been published elsewhere.  database of privately and publicly funded clinical studies conducted around the world.

EU Clinical Trials Register: information on interventional clinical trials on medicines conducted in the European Union (EU), or the European Economic Area (EEA) which started after 1 May 2004.

WHO International Clinical Trials Registry Platform: access to information about ongoing and completed clinical trials. It provides a searchable database containing the trial registration data sets made available by data providers around the world 

Cochrane CENTRAL: The Cochrane Central Register of Controlled Trials (CENTRAL) is a source of reports of randomized and quasi-randomized controlled trials. Most CENTRAL records are taken from bibliographic databases (mainly PubMed and Embase), but records are also derived from other published and unpublished sources, including and the WHO's International Clinical Trials Registry Platform.

If you are using grey literature as sources for your medicine and health related research, you may also be interested in taking a look at the Finding and using evidence for clinical practice tutorial and/or the Systematic Review LibGuide.

Finding and using evidence for clinical practice tutorial

Systematic Review LibGuide




There are a range of sources you can use to identify grey literature in health and social care. Grey literature in health and social care includes government or nongovernment reports, unpublished studies and conference papers and papers from think tanks and charities.

Sources include:

The Census (UK) is undertaken by the Office of National Statistics (ONS). Census data is available to academic institutions via the UK Data Service. Data available includes population, flow and boundary data, and major collections of government statistics and social data. Data can be filtered by theme, geography and key data.

The Census Data LibGuide provides guidance on finding and using Census Data and the UK Data Service.

Finding and using research datasetsThe Finding and using research datasets guide has been designed as a starting point for students and researchers looking to explore datasets in their subject discipline. 

If you are looking for general datasets, try the 'Interdisciplinary research' section, otherwise select the subject that is most relevant for the topic you are researching. 

The following resources provide access to several types of company information:

Company data and documents:

- Companies House (UK)

-US Securities and Exchange commission (US)

Please note: the following resources are for education and research use only, they are not for commercial use.

Company news and media coverage:

Visit our Finding Company Information tutorial, for online guidance on selecting and using company information sources.


Please note: these resources are for education and research use only, they are not for commercial use.

Exeter's digital resources provide two main types of market research information:

  • industry research
  • information on the broader business and economic environment.

Resources specialising in industry research will usually provide profiles with data and analysis on on individual sectors. Profiles will often focus on industries within the context of a specific country. 

Resources that include information on the wider business and economic environment will also present their information in the form of 'economic profiles', usually focusing on international regions, countries or cities. Most resources will provide a mix of statistics, analysis and demographic information.

Click on the Finding Market Research tutorial opposite, for online guidance on selecting and using company information sources

A patent is a legal contract and intellectual property (IP) right which protects a new invention, by giving the owner the right for a limited period of time to prevent others from exploiting the invention without permission. It means that the invention cannot be commercially made, used, distributed or sold without the patent owner's consent.

It gives a detailed and technical description of the invention, and as such contains much information that may never be published in any other format. A patent is generally applied for at the earliest possible stage of an invention; it thus often provides the newest information available in a field, before journal articles are published or new products reach the market. 

Find out more about searching for patent information in our Patents LibGuide

A standard is a published specification that establishes a common language and an agreed, repeatable way of doing something. It contains a technical specification or other precise criteria and is designed to be used consistently, as a rule, a guideline, or a definition.

Standards are applied to many materials, products, methods and services. They are designed for voluntary use and do not impose any regulations. However, laws and regulations may refer to certain standards, making compliance with them compulsory.

Find out more in the Standards LibGuide

The University has a subscription to British Standards Online (BSOL) It is a bibliographic, citation and full-text database of more than 90,000 standards in the subject areas of Health and Life Sciences and Science, Engineering and Technology, including business, commerce and finance, construction, electrical and electronic engineering, healthcare and medical devices, manufacturing, and mining and minerals.  

Statistics is the science of collecting, analysing and presenting numerical data and can be a vital source of information for your studies.

Statistical data can be found on a huge variety of subjects including:

  • the economy
  • employment
  • the environment
  • government
  • health
  • international trade
  • manufacturing
  • population

A wide range of data and statistical sources are available via the university. Many organisations and governments also make statistical data freely available via their websites.

Use the Finding Statistics: Quick Guide for more information.

For guidance on databases relevant to the science of statistics and statistical computation take a look at the Mathematics and Computer Science LibGuides.

Social Media blogs, twitter feeds, email discussion lists etc. can be useful research resources.  

For example, they can highlight key topics and debates that are live at particular points in time.  Also many experts and organisations use these communication methods to highlight larger research projects and work.

As is the case with website information, it is vital that you evaluate these resources as the quality and reliability of information will be highly variable.

The information may be available fleetingly as blogs and twitter feeds come and go, so make sure you capture any material you want to use in your research in case it is deleted during the course of your research activities.

As with news, not all kinds of social media communication would be considered grey literature but they may still be useful in leading you to other types of grey literature such as working papers, research findings and results, speeches, interviews etc that are flagged or discussed. For example, the medical profession has long considered the value of "evidence-based tweeting" as a mechanism for improving the outreach and dissemination of health and medicine related research outcomes and finding. 

See: Social Media, Evidence‐Based Tweeting, and JCEHP - Djuricich - 2014 - Journal of Continuing Education in the Health Professions - Wiley Online Library  

Discovery Tools for Grey Literature

You may need to use a variety of different types of information tools to discover grey literature in your research field.  For example:

  • Databases: news, official publications, market research, annual reports, research reports, patents and standards, conference proceedings, statistics
  • Library catalogues: theses, dissertations, official publications, research reports
  • Online repositories:  theses, dissertations, research reports, pre prints, trials
  • Organisational websites: annual reports, market reports, speeches, working papers, discussion papers, policy statements, government reports, newsletters, statistics
  • Internet search engines: this is the broadest category and will lead you to all forms of grey literature but can be particularly useful for things like blogs, twitter, wikis, presentations, email lists etc. that you may not find via other routes.

Tip: It can help to capture your searching activity, using a table or spreadsheet. This will enable you to rerun searches later and will also help you identify which resources are useful for which topics. Capture:

  • Search tools used
  • Search terms and techniques
  • Useful organisational websites and databases

General Database Searching 

Many of the research databases include grey literature materials such as conference papers, government documents, dissertations, newsletter etc. alongside the more traditional publisher controlled literature such as books and journals.

Keep a look out for a publication or source type filter when searching or viewing your search results so that you can restrict your search to grey literature type content.  

See example opposite for filters available in the Proquest Premium Business Collection.

Use your Subject Guide to discover the recommended research databases for your discipline.

Key Grey Literature Databases

See the Overton guide for more information on this database.

Specialist Databases

There are also various specialist databases where you will find different types of grey literature sources.  For example, there are services dedicated to official publications, news, market research, standards and clinical trials etc. 

See the guidance below for recommended specialist databases for the different types of grey literature materials.

Library Catalogues will include some forms of grey literature, e.g. , government reports, statistics, working papers and conference papers.

You can search by known information such as authors or the title of documents, and can also search by organisational name to find things like conference papers and working papers from particular organisations.

You can also search more widely by using relevant subject keywords and then add terms such as report, paper, proceedings order to focus in on grey literature type publications.  

You can use the following services to search across library collections:

  • Library Hub Discover: Search and locate books and journals throughout the collections of the UK research and specialist libraries.
  • WorldCat: Search the collections of thousands of libraries worldwide. 

A variety of grey literature is held in online repositories where researchers and organisations post their work for archiving and discovery purposes.There are a range of different types of repositories.

Institutional Repositories

Many academic bodies have institutional research repositories where academics and students post their papers, articles, books etc.

For example, ORE is the University of Exeter research repository.

Subject based Repositories 

​Subject repositories are digital collections of the research outputs within particular subject areas which have been created and developed over time to meet the needs of specific research communities. They promote the rapid dissemination of research findings

Some act as an archive for early drafts of research papers, which are subject to comment and amendment before appearing as final published articles.  These are often referred to as 'pre-print archives' or 'pre print repositories'.

You should check for a subject repositories in your research area as they can be a good way of finding the very latest research papers and discussion on a topic. 

Examples include; Covers:  Physics, mathematics, computer science, quantitative biology, and statistics.

bioRxiv The preprint server for biology

Social Science Research Network (SSRN). 

Grey Literature Repositories

You can also look at repositories dedicated to the archiving of grey literature materials.

OpenGrey : OpenGrey is a multidisciplinary European database, covering science, technology, biomedical science, economics, social science and humanities. Document types include technical or research reports, doctoral dissertations, conference papers, official publications, and other types of grey literature.

Grey Guide Portal: Repository and Portal to Good Practices and Resources in Grey Literature.  Part of the GreyNet International Grey Literature Network Service.

You can target the websites of relevant organisations in order to access the content they post on the web, that might not otherwise be published.

Build up the list of sites you want to visit and search regularly.  They might be:

  • Companies
  • Government Departments
  • Think Tanks
  • Research Organisations
  • Professional Bodies


  • Search for your topic using a search engine and and look through the first few pages of results to get an idea of relevant organizations, think tanks, groups or other relevant websites to target
  • Use the search box on the website to find information of interest
  • Look out for sections such as Publications, Reports  Library etc. where grey literature items might be held. It may be quicker and more effective to search this section that the entire website
  • Some sites have RSS feeds where you can sign up to receive updates by email
  • Remember to save a copy of information you source via websites as the information may be taken down later

Internet Archive: Wayback Machine

The Internet archive can sometimes help if you are trying to trace information that was posted on an organisational website and is no longer available.  You can enter a web address to check and see if earlier versions of that site were captured on a particular date.  Click on a date to view the site as it appeared then.

Example shows the University of Exeter website snapshot archive.

If you know particular findings or other announcement was made by an organisation on a particular date - this archive tool may help you trace details. 

You may need to do further work to trace referenced materials as the full text may no longer be publicly accessible via the web.


Web search engines can be used to locate grey literature not published within academic databases or via other formal publication routes.

Take advantage of advanced search options offered by the search engines in order to focus your search and target grey literature.

For example Google's Advanced search has a number of options that can help improve searching. The most useful options are flagged below.


  • Find pages published in a particular region.
  • Useful looking at impact of topics and research in different areas of the world
  • Select from the drop down menu

Site or domain

  • Search across a website (will only work for website which Google can crawl)
  • Search one site (like ) or limit your results to a domain like .edu, .org or .gov
  • Just add your site/domain to the search box
  • You can view a list of different counties URL and domains here.

Terms appearing

  • Search for terms in the whole page, page title or web address, or links to the page you're looking for.
  • Select an option from the drop down menu

File Type

  • Search for pages in the file format that you prefer.
  • Select an option from the drop down menu
  • Includes the following which can be useful for grey literature materials
  • Adobe Acrobat PDF
  • Mitrosoft Excel / Word/ Powerpoint


You can also use these options with their search operators within the usual search box rather than using the advanced search and drop down menus, e.g, intitle:climate change filetype:pdf


Google Scholar

Searching Google Scholar in a systematic way can be difficult due to an absence of advanced search options and filters. You can complete a search on Google Scholar using Boolean login (AND/OR) and use many of the same search techniques (i.e truncation) as you would in other databases, however you are likely to recall a very large number of results.

The paper below discusses how Google Scholar can be used in evidence reviews, with a particiular focus on identifying grey literature. Due to the large number of results provided by the search engine, the authors suggest focusing on the first 200-300 results as Google uses a relevancy ranking system which in theory should place the most relevant results within the first few pages. If you choose to do this, you can make it clear that you have done this in your review methods.

Haddaway NR, Collins AM, Coughlin D, Kirk S (2015) The Role of Google Scholar in Evidence Reviews and Its Applicability to Grey Literature Searching. PLoS ONE 10(9): e0138237.

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