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Systematic Reviews

Data Collection - The Literature Search

The literature search is the most important part of a systematic review (Campbell Collaboration)
  • The literature search is how you obtain your data for your study
  • The goal of the literature search is to find all relevant studies including:
    • Traditional peer reviewed literature
    • Grey literature
The systematic review literature search must:
  • Be well documented
  • Be transparent and reproducible
  • Include a diversity of resources
  • Be iterative

Search Strategy

Search Strategy
  • Key concepts to be searched (PICOS if using)
    • How are these terms represented in different disciplines?
    • What are related terms / synonyms? Be as comprehensive as possible
    • What are the subject headings (e.g. MeSH) in each database?
  • Review known relevant articles to determine keywords and subject headings
  • Review previous relevant systematic reviews for possible strategy
    • Is there a Cochrane group that has recommended terms

Search Strategy

Example of Search Concepts

Brainstorm synonyms for each search concept, as illustrated below.

Boolean: OR synonyms and AND search concepts




selective serotonin reuptake inhibitor*


serotonin update Inhibitor


5-ht update inhibitor*





infantile autism


autistic disorder












Data Sources

  • Databases
  • Reference searching
  • Cited by (forward citations searching, citation pearl growing)
  • Contact with experts
  • Hand searching key journals, journals with poor/no indexing
  • Grey literature


Ask yourself: which disciplines inform my research


Educational interventions for young adults with ASD for gaining employment
Disciplines that might inform this topic include then review the databases withing each discipline
  • education
  • business
  • social work
  • psychology


Different interfaces require different searching techniques



Sample Grey Literature Resources

Data Collection - The Literature Search

  • Consult with your subject liaison librarian
  • Document, Document, Document
    • Databases searched, date range searched, date last searched
    • All search terms for each database, as far as possible
    • Follow the PRISMA flowchart (or other reporting guidelines -- refer to Reporting Findings)
      • Number of hits for each database searched
      • Duplicates within databases

Search Strategy

Search Strategy
  • Use truncation
    • nurs* will retrieve: nursing, nurse, nurses, nurses, nursed, etc
  • Use both free text (keywords) and subject headings when possible
  • Pilot your search strategy
    • Is your search retrieving the known articles?
    • If no, why not?
      • Check indexing
      • Check truncation
      • Check free text keywords
      • Check descriptors / subject headings
  • It takes a LOT OF TIME

Saving Your Search

  • Save your searches in each database
    • Create an account within the database interface
    • Label the search clearly (is it a draft, final, date, database name)
  • Keep detailed records of all searches conducted:
    • Month, date, year of search
    • Database searched
    • Exact search strategy
    • Any limits used (year of publication, language, etc)
    • Number of hits for each database
  • Remember – goal is to report search strategy in a transparent manner so that it can be replicated

Grey Literature

  • publicly available, foreign or domestic, open source information that is usually available only through special channels and may not enter normal channels or systems of publication, distribution, bibliographic control, or acquisition by book sellers or subscription agents (U.S. Interagency Grey Literature Working Group 1995).

Locating Grey Literature:

Consider what types of organizations or associations are likely to be interested in the same research question:
  • Government agencies / NGO agencies
  • Government departments
  • Industry, trade, professional organizations
  • Advocacy groups
  • Private agencies

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