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How to Write a Literature Review: Phrases

This guide will assist in the development and structure for writing a literature review in a health sciences discipline

Basics of phrase searching

  • Some databases assume that words typed next to each other should be searched as phrases.
  • Others automatically put a Boolean AND between your search terms, requiring that all the words be present, but not necessarily adjacent to each other.
  • These searches can retrieve very different results.
  • Using parentheses or quotes around search words is a common way to do phrase searching, but not all databases or search engines use them.


"genetic engineering" or (genetic engineering)

Proximity search basics

  • Many databases allow you to specify that the words you are searching are within a certain proximity of each other.
  • Because of their proximity the two words can have a relationship
  • Proximity operators are more specific than Boolean operators and make your search more precise.
  • Proximity operators also vary by database, but some common ones include: W# (With, Within) and N# (Near).
    • W# can specify that words appear in the order you type them

      • Substitute the # with a number of words that may appear in between. If no number is given, then it specifies an exact phrase.

    • Example: 
      cold W2 therapy, it retrieves: cold therapy, cold water therapy, etc.)

    •  N# can specify that the words may appear in any order.

      • Substitute the # with a number of words that may appear in between.

    • Example:
       cloning N3 human, it retrieves: cloning of humans, human cloning etc.)

  • Proximity Operators vary from database to database (ADJ#, W/#, N/#, NEAR#, etc), you need to check the Help section of each database to see what they use, look for Proximity Operators or Proximity Searching

Search Map Revised for Proximity Searching

See original Search Map

Example: What is the risk of mortality due to cell phone use in distracted teen drivers?









(cell OR cellular OR smart OR mobile) ADJ1 (phone OR phones)









(distract* OR inattent*) ADJ2 
(driver* OR driving)

Parentheses are extremely important in proximity searching.  Using parthentheses the search would look like this:

​(mortal* OR fatal* OR deathAND ((cell OR cellular OR smart OR mobile) ADJ1 (phone OR phones) OR smartphone* OR cellphone*AND ((distract* OR inattent*) ADJ2 
(driver* OR driving))

 The asterisk at the end of some words is a wildcard which is used to find alternate endings, see Truncation for more information. 

Medline (OVID) Search using proximity searching with ADJ

See original search in PubMed without proximity operators. Note: the original search in PubMed retrieved 6 results where this search in OVID Medline with proximity operators retrieved 34. As a reminder PubMed and MEDLINE are essentially the same databases.

MEDLINE OVID - Search History - showing distracted driving and cell phone use with proximity operator ADJ


Consult a Health Sciences Librarian


Neil John Maclean Health Sciences Library (University of Manitoba) --- ph. 204-789-3342 |