Skip to Main Content
Purdue University Purdue Logo Purdue Libraries

SURF Introduction to Literature Reviews

Develop search strategy and maintain citations

Developing a Database Search Strategy

A search strategy is the combination of keywords and synonyms you choose and the way you connect them with AND, OR, and NOT.  These are also known as Boolean operators. An example search strategy can be found near the end of this page. Developing good search strategies helps increase the efficiency and effectiveness of your database searches.

To focus your search and ensure you are getting sources that combine all aspects of your topic, use AND. Adding terms with AND will give you fewer results.

For example, car AND hydrogen AND environment will find sources that use all three of these terms.

Venn diagram highlighting overlapping section of car and hydrogen and environment


To expand your search and find sources that use different words for the same thing, use OR. Adding terms with OR will give you more results.

For example, car OR vehicle or automobile will give you sources that use any of these terms, alone or in combination with each other.

Venn diagram highlighting all three circles - car, vehicle, and automobile


To omit certain terms from your results, use NOT. For example. You may have done an initial search and found that many of the sources you found are related to Ford. This is great, but you are interest in other car manufacturers too.  You want to filter out the articles about Ford so you can only see the ones about other manufacturers. 

For example, car NOT Ford will discard any of the articles that mention Ford.

Overlapping circles that highlights only the left half for car, not the overlapping part or the Ford half


Other search tips:

  • Many databases use an asterisk (*) to truncate words if you want to search for all words with that root.  For example, *environment would search for environment, environmental, environmentalism, ect…
  • Put quotes around a phrase that you want the database to search as a phrase, rather than as individual words.
  • Group synonyms inside parentheses using OR between each one.

Search strategy example: using the example keywords and synonyms below, one search strategy might be:

(car OR automobile OR vehicle) AND hydrogen AND environment*

search strategy for (car OR automobile OR vehicle) AND hydrogen AND environment*

Database Search Help

Different databases may utilize distinct search functionalities and features. To maximize the effectiveness of your searches it is helpful to spend some time exploring the "Help" or "Support" information provided. For example, here is a screenshot of the help information available in Engineering Village.  Notice there is a great deal of information pertaining to the database's "Search" functionalities.

Engineering Village screenshot

CRAAP Test

Using the CRAAP Test

Evaluation Criteria

Currency: The timeliness of the web page.
  • When was the information gathered?
  • When was it posted?
  • When was it last revised?
  • Are links functional and up-to-date?
  • Is there evidence of newly added information or links?
Relevance/Coverage: The uniqueness of the content and its importance for your needs.
  • What is the depth and breadth of the information presented?
  • Is the information unique? Is it available elsewhere, in print or electronic format?
  • Could you find the same or better information in another source? For example, a general encyclopedia?
  • Who is the intended audience? Is this easily determined?
  • Does the site provide the information you need?
  • Your overall assessment is important. Would you be comfortable using this source for a research paper?
Authority: The source of the web page.
  • Who is the author/creator/sponsor?
  • Are the author’s credentials listed?
  • Is the author a teacher or student of the topic?
  • Does the author have a reputation?
  • Is there contact information, such as an e-mail address?
  • Has the author published works in traditional formats?
  • Is the author affiliated with an organization?
  • Does this organization appear to support or sponsor the page?
  • What does the domain name/URL reveal about the source of the information, if anything?
  • example: .com .edu .gov .org .net
Accuracy: The reliability, truthfulness, and correctness of the informational content.
  • Where does the information come from?
  • Are the original sources of information listed?
  • Can you verify any of the information in independent sources or from your own knowledge?
  • Has the information been reviewed or refereed?
  • Does the language or tone seem biased?
  • Are there spelling, grammar, or other typographica errors?
Purpose/Objectivity: The presence of bias or prejudice/The reason the web site exists.
  • Are possible biases clearly stated?
  • Is advertising content vs. informational content easily distinguishable?
  • Are editorials clearly labeled?
  • Is the purpose of the page stated?
  • Is the purpose to inform? teach? entertain? enlighten? sell? persuade?
  • What does the domain name/URL reveal about the source of the information, if anything?
  • example: .com .edu .gov .org .net Chico