Systematic and other major reviews involve a comprehensive search of the literature to ensure all studies that meet the predetermined criteria are identified. Typically, key subject databases are searched first, after which the team might turn to less conventional search venues and explore what is known as grey literature - essentially any research that is shared outside of traditional publishing and distribution venues. Examples of grey literature include white papers, working papers, reports, dissertations, government documents, and policy documents. And after screening the results found through these means, engaging in citation searching is recommended (see below).
Review teams should develop search strategies that incorporate a mix of keywords and controlled vocabulary specific to the databases they're searching. Controlled vocabulary like the Medical Subject Headings (MeSH) used by PubMed and MEDLINE are standardized words and phrases that help enable the organization and retrieval of information in databases and other online venues.
Each research question is different, so the terms you use and the number and types of databases you'll search - as well as other online publication venues - will vary. Some standards and guidelines specify that certain databases (e.g., MEDLINE, EMBASE) should be searched regardless. Your subject librarian can help you select appropriate databases to search and develop search strings for each of those databases.
Since systematic reviews began in the health sciences, searching PubMed, MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials is standard practice. These databases are listed below.
However, if you are conducting a review of the literature in another discipline, you will need to search the databases specific to that discipline. To begin, consult the library's complete list of databases or speak with your librarian.
PubMed is the National Library of Medicine's interface for MEDLINE, and also includes in-process and pre-1966 citations and other resources outside of MEDLINE. While basic PubMed is free to all Internet users, this link adds "Find it" buttons to individual citations that connect to the University of Nevada, Reno Libraries' journal subscriptions and document delivery services for full-text options.
Updated daily, MEDLINE on the Ovid platform offers searchers seamless and up-to-the-minute access to over 23 million of the latest bibliographic citations and author abstracts from more than 5,600 biomedicine and life sciences journals in nearly 40 languages (60 languages for older journals). English abstracts are included in more than 80% of the records. Coverage dating back to 1946.
An Elsevier database that covers the same subjects as PubMed/MEDLINE, with an additional focus on drugs and pharmacology, medical devices, clinical medicine, and basic science relevant to clinical medicine. 1947 - present (selectively back to 1902).
The Cochrane Library contains the Cochrane Database of Systematic Reviews (CDSR), Cochrane Central Register of Controlled Trials (CENTRAL), and Cochrane Clinical Answers that offer different types of high-quality, independent evidence to inform healthcare decision-making.
Several online tools exist to help you identify controlled vocabulary, develop better search strings, and "translate" a search string developed for one database into one that works in another database. The tools listed below can assist you with one or more of these tasks. However, they are primarily aimed at and designed for teams and databases working in the health sciences.
As noted above, searching the grey literature is also a key component of a good systematic review strategy. However, where to search for such sources can vary a lot depending on the topic or field. Many researchers make use of the resources listed below. Please consult your librarian for more targeted assistance.
Citation searching is a method of searching the literature using citations rather than going to a database and conducting a search using keywords. It can help you better understand the scholarly landscape within your discipline and determine how your own work fits within that landscape. There are two types of citation searching: backward searching and forward searching.
When reading a work that’s very relevant to your research, you may want to examine the reference list closely to see which previously published works influenced the author(s). If you tracked down those cited works, you’d be engaging in what is known as backward citation searching.
Conversely, you may want to determine whether and by whom a given work has been cited after its publication – essentially, you’re wanting to know if other, newer works have included it in their reference lists. This is called forward citation searching.
The resources listed below can help you with citation searching.
Provides a search of scholarly literature across many disciplines and sources, including theses, books, and articles.
This collection contains over 21,000+ journals from 1900-present and includes: Science Citation Index, Social Sciences Citation Index, Arts and Humanities Citation Index and others. Search by subject, author, or cited reference. An excellent current awareness and bibliography-building tool.
