According to Paez A (2017), "...gray literature, or evidence not published in commercial publications, can make important contributions to a systematic review. Gray literature can include academic papers, including theses and dissertations, research and committee reports, government reports, conference papers, and ongoing research, among others. It may provide data not found within commercially published literature, providing an important forum for disseminating studies with null or negative results that might not otherwise be disseminated. Gray literature may thusly reduce publication bias, increase reviews’ comprehensiveness and timeliness, and foster a balanced picture of available evidence."
According to Lawrence et al (2015)"..The internet has profoundly changed how we produce, use and collect research and information for public policy and practice, with grey literature and data playing an increasingly important role. Reports, discussion papers, briefings and many other resources produced and published by organisations, without recourse to the commercial or scholarly publishing industry, are a key part of the evidence used for public policy and practice. Yet finding and accessing this material can be a time-consuming task made harder by poor production and management of resources and the lack of digital collecting services. Even knowing what is being collected and what collections exist is a difficult task. Based on research conducted as part of the Grey Literature Strategies ARC Linkage project, this article reports on the results of online surveys of users, producers and collectors of policy and research information with a particular focus on the results for collecting services...".
According to Rucinski (2015)"...literature that ‘falls through the cracks’ or as little literature, typical examples of grey information resources include corporate documents, discussion papers, in-house journals and newsletters, surveys, working papers, technical reports, trade association publications, institutional or association reports and bulletins...conference proceedings, academic and government reports. Others have included in the grey literature category unpublished manuscripts . . . product catalogs . . . presentations, personal communications, pre-prints, academic courseware, lecture notes, and so on."
According to Dominic Farace, Director at GreyNet International: "...Grey literature has over the past half-century been identified by a number of terms and concepts. For example, non-conventional, unconventional, or non-commercial literature. These are accepted but limited descriptors. Other examples that are less accepted and rather off-the-mark are terms such as ephemera, fugitive or non-published literature. For many years, attention was only placed on the demand-side for grey literature and not on the supply or production side. Since the launch of the International Conference Series on Grey Literature in 1993, the results of research in this field of library and information science has contributed to a fuller understanding of the production, publication, open access, as well as uses and applications of grey literature. Likewise, the misnomer that grey literature was but the antipathy of commercial literature needed to be addressed and corrected. This could only be achieved on a more level playing field. Grey literature stood much to gain from the methods of commercial publishing, while commercial publishing stood to gain from the richness and diversity found in grey literature. This richness and diversity can be seen by the hundreds of document types in which it is published both in print and electronic formats. It can also be viewed by the range of corporate authors (organizations in government, academics, business and industry) that publish it; and by the wide range of professional, scientific, and technical communities that contribute to its research, authorship, and review. Where once grey literature circulated primarily within communities and networks of interested professionals, now – owing to the internet and open access policies – grey literature is today accessible to net-citizens i.e. the broader public... "
"...grey literature publications are non-conventional, fugitive and often ephemeral. They may include but are not necessarily limited to the following types of materials: reports (pre-prints, preliminary progress and advanced reports, technical reports, statistical reports, memoranda, state-of-the art reports, market research reports, etc.), theses, conference proceedings, technical specifications and standards, non-commercial translations, bibliographies, technical and commercial documentation, and official documents not published commercially (primarily government reports and documents)". — Alberani, 1990
Grey literature may be defined as the type of documents written and published for a very limited niche audience, certainly outside of all major distribution channels and often difficult to find in the most commonly-consulted bibliographic databases. This literature is expanding exponentially and may include presentations at conferences, health technology assessments done by hospitals, and certain government documents. In 2016, there is a lack of unanimity on the definition of grey literature, as its boundaries continually shift and evolve as new technical means are developed.
Explosive growth of the web has had a huge impact on production, access and distribution of grey lit such that "the difficulty of retrieval, which used to be a distinctive feature of grey literature . . . is now minimized."
Definition:An ill-defined area that does not readily conform to an existing category or set of rules - Oxford English Dictionary
Grey literature is used to describe materials not published commercially or indexed by major databases.
GL may be of questionable relevance or quality but may still have an impact in research, teaching and learning.
GL is occasionally the only source of information for specific research questions. While some GL may be published eventually, and may be easier to find, sometimes it never is.
GL may not go through a peer review process, and its authority must be scrutinized.
"Fugitive", hidden, invisible or literature in the deep web may be on government sites, deep in archives, institutional repositories, theses databases, conference sites, associations.
Informal communication is changing the notion of grey literature which is expanding to include e-mails, faxes, blog postings, wikis, RSS feeds and podcasts.
What differentiates traditional GL from other published literature?
Historically, the publication of GL has not been considered part of traditional publishing channels and models; consequently, it is not always considered to be valuable in the research process.
Producers of GL include research groups, non-profits, universities and government departments, to name a few but in the digital age just about anyone ("wisdom of crowds") can be producer of content.
Grey literature is historically differentiated as not widely-disseminated or promoted, due to its producers being outside the traditional publishing mainstream.
Wide dissemination of published materials is the goal in traditional publishing; infrastructure exists to disseminate this material to make it visible, marketable and "findable".
The web is changing dissemination and publishing processes. However, findability remains difficult, but this is even true for the white literature.
It is important to note that grey literature provides a range of perspectives in research, both quantitative information but also provides valuable qualitative knowledge in some areas. Grey data can be derived from different contexts providing a more balanced view of a problem; the question is whether the value resides in the analytical-integrative aspects or the aggregative-quantitative aspects.
Insignificant results in some empirical work are known to be under-represented in the international peer-reviewed journal literature; by including grey literature in synthesis, the resulting studies are more likely to decrease the effect of the studied factors, but provide a more representative picture of the system being analyzed.
Some examples of non-traditional publishing
Some organizations create their own reports, studies, etc. This is increasingly true in web 2.0.
Think of health organizations that publish their own studies, such as the Canadian Cancer Society and the Heart & Stroke Foundation
Librarians try to adopt pro-active approaches to finding locally-published materials, though web-based searching, self-archiving and open access
Specialized strategies are needed to facilitate identification and retrieval of grey literature
The field of GL has evolved into a world of its own with specific research methodologies, vocabularies, systems and solutions. Before exploring these methods, let's highlight some of the work that health librarians are doing in this area.
librarians and information specialists are the acknowledged experts in searching.
several experts write regularly about searching for the grey literature. SeeWho is who in GL?
Julia Gelfand is an applied sciences librarian at the University of California who has studied grey literature for many years and presented at international GL conferences. Her research includes searching, preservation issues and scholarly communication.
Search engines help uncover a ton of grey literature. Banks says that the barriers to grey literature are coming down as a result of open access and search engines. Search expert and librarian, Gary Price, says that 'public information on the deep web is currently 400 to 550 times larger than the surface Web'. In light of institutional repositories and open archives the deep web is more accessible than ever but much continues to be locked away behind commercial (or password-protected) databases.
Health literature fares better than some areas. But conference proceedings, abstracts and government reports in the pre-digital era are difficult to locate. The web provides access to a trillion+ pages of content, but not all relevant information is digitized yet. Librarians should work towards improving access to older materials which are, mostly, grey literature.
Some places where grey literature is abundant
Work done at the PhD-level requires exhaustive searching for hard-to-find materials
Systematic reviews, clinical trials and in-house research that cover health and wellness issues
Most advanced research done at universities, medical schools and health organizations
Environmental organizations, engineering publications and newsletters, conservation resources
Geological and geophysical surveys, maps, fossil records, locations of minerals and ores
Grey literature in technical fields, aeronautics and engineering may include contractor and technical reports, product codes and standards, special publications, handbooks and patents
Effective searching is a professional skill undertaken by librarians and information specialists. The aim of searching in the health sciences is to be as thorough as possible and to optimize recall with sufficient precision. Researchers doing systematic reviews (SRs) or meta-analysis should ensure that all relevant studies are found. The focus is on exhaustiveness and leaving no stone unturned. Reviews are useful tools for health professionals in view of the massive amount of biomedical information published worldwide as they are a useful distillation of evidence.
It is imperative that health librarians create search strategies and execute them accordingly. When a structured search is not performed, search results may be affected. Studies in other languages or those not indexed by major tools must also be located to avoid skewed results, and publication bias. In a recent study, it was estimated that an additional 29.2% items were found by using extended search methods in addition to mainstream sources. (seeSavoie et al).
Some researchers suggest that SRs that include grey literature of uncertain quality may actually jeopardize the findings of reviews. This is where rigorous inclusion criteria can ensure that only truly relevant studies make it into the final analysis. It is a common occurrence that high numbers of studies retrieved by the librarian may not make it into the final review assessment.
Open Access (OA) to materials and the creation of institutional repositories has revolutionized publishing and the work of providing access to published works. Despite pivotal information trends like these, some digital and print materials are still hard to find and obtain. All librarians and information specialists have personal stories about finding elusive conference proceedings, abstracts and reports. The digital age has not completely changed that - not yet in any case.
The emergence of search engines has helped to index (and make findable) a lot of GL. But searching carelessly with Google creates other problems for information specialists as important documents can easily be missed. Even though the Web is estimated to be 500 billion - perhaps as high as one trillion pages, its functionality as a search space is limited due to its methods of organization.
Computer algorithms help to improve search engines. Pagerank uses popularity as a means of ranking results with important items rising to the top. But by placing popular materials at the top of results, searchers will rarely beyond the first six or seven results.
As librarians know, relying on popular documents that rise in search results is not a recommended strategy. Important documents may be easily retrieved via search engines, but some GL may ultimately be hidden within results, down several pages or not visible at all due to a relative lack of popularity. (Other trends to watch: collaborative writing/publishing via Wikis and blikis.)