When conducting a systematic review, it is imperative to brainstorm a list of keywords related to your topic. Examining the titles, abstracts, and author-provided keywords of pertinent literature is a great starting point.
Things to keep in mind:
When searching chemical compounds, use a chemical data resource, such as PubChem, to identify all possible synonyms.
Boolean searching yields more effective and precise search results. Boolean operators include AND, OR, and NOT. These are logic-based words that help search engines narrow down or broaden search results.
The Boolean operator AND tells a search engine that you want to find information about two (or more) search terms. For example, sustainability AND plastics. This will narrow down your search results because the search engine will only bring back results that include both search terms.
The Boolean operator OR tells the search engine that you want to find information about either search term you've entered. For example, sustainability OR plastics. This will broaden your search results because the search engine will bring back any results that have either search term in them.
The Boolean operator NOT tells the search engine that you want to find information about the first search term, but nothing about the second. For example, sustainability NOT plastics. This will narrow down your research results because the search engine will bring back only resources about the first search term (sustainability), but exclude any resources that include the second search term (plastics).
Most databases offer a thesaurus, controlled vocabulary, or list of available subject headings that can be assigned to an article by the author or indexer.
Use of the preferred term is a powerful and controlled way of directly accessing most if not all of the material within a field of study. Each is a hierarchical arrangement of broader terms, preferred and related terms, and narrower terms, designed to map the context and content of their respective fields.
Web of Science's Core Collection offers a list of subject categories that are searchable by the Web of Science Categories field.
When in doubt, reach out to a librarian! We are highly skilled in effective searching and creating search strategies, from simple keyword searches to several-paragraph-long search strings.
Reach out to a Duke University Libraries librarian at asklib@duke.edu or use the chat function.
Grey literature is information produced outside of traditional academic publishing and distribution channels. Examples of grey literature include reports, working papers, theses and dissertations, policy literature, newsletters, government documents, conference proceedings, and white papers.
The intent of a systematic review is to synthesize all available evidence that is applicable to your research question. There is a strong bias in academic publishing to only include peer-reviewed content in systematic reviews. However, grey literature allows access to diverse evidence sources and reduces risk of publication bias, While not peer-reviewed, grey literature represents a valuable body of information that is critical to consider when synthesizing and evaluating all available evidence.
Adapted from Cornell's guide on grey literature. Please visit for more information.
National Technical Reports Library (NTRL)
The National Technical Information Service acquires, indexes, abstracts, and archives the largest collection of U.S. government-sponsored technical reports in existence. The NTRL offers online, free and open access to these authenticated government technical reports.
Federal rulemaking portal that houses all documentation related to policy creation.
Created by the U.S. Environmental Protection Agency, ChemView improves access to health and safety data on chemicals regulated under the Frank R. Lautenberg Chemical Safety for the 21st Century Act which amends the Toxic Substances Control Act (TSCA). It contains information EPA receives and develops about chemicals.
Institutional Repositories
Most universities have institutional repositories that house electronic copies of theses and dissertations published by their students. To find these digital repositories, navigate to a university's library website and search for theses / dissertations. While many are freely available, especially those published more recently, some are still behind paywalls.
Inclusion: Everything that a study must have in order to be included in your review.
Exclusion: Factors that would make a study ineligible to be included in your review.
Inclusion / exclusion criteria should be determined after defining your research question but before the search is conducted. In some cases, scoping reviews should be undertaken first to determine appropriate criteria. Remember, these criteria must be clearly defined.
Be aware that you may introduce bias into the final review if these are not used thoughtfully and adhered to regardless of outcome. The purpose of using inclusions / exclusion criteria "is to minimize ambiguity and reduce the possibility of poor reproducibility."
McDonagh M, Peterson K, Raina P, et al. Avoiding Bias in Selecting Studies. 2013 Feb 20. In: Methods Guide for Effectiveness and Comparative Effectiveness Reviews [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2008-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK126701/
