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Conducting a Literature Review

Deleting Duplicates

When searching multiple databases, it is very common to retrieve duplicate citations. Importing your search results into Zotero, EndNote or a similar tool can simplify deleting duplicates. Record the number of duplicates that you delete

Deduplication with EndNote

Option 1: Select the References menu, then Find Duplicates. A window will appear showing a side by side comparison of duplicates. Any differences between records will be highlighted. You may copy information from one record to another. Select Keep This Record for one and the other will be sent to the Trash or select Skip to keep both. 

Option 2: Select the References menu, then Find Duplicates. Select Cancel on the appearing window to see a list of duplicates. The newer versions of each duplicate will be highlighted. You may drag the highlighted references to the Trash (on the left).

After completing Option 1 or 2, sort All References by author or title to identify any remaining duplicates. You may change the default deduplication settings by selecting the Edit menu, Preferences, then Duplicates.

Screening the Results

After deduplication:

1. Screen your search results by title and abstract, focusing on reasons to exclude rather than include studies, which may help to complete the process quicker.

2. Screen by reading the full texts, removing studies or other materials that do not meet your inclusion criteria.

Some reviewers also choose to "hand search" the reference lists of included studies for additional studies.

Keep track of the number you exclude at each level. At the full-text screening level, it is also common to keep track of your reasons for excluding each paper.


A free, web-based tool that is highly recommended for screening at both the title/abstract and full-text level. Keep in mind:

  • It offers a blinding option when shared with other reviewers. 
  • The deduplication feature is still under development, so first dedup using other software before importing results. 
  • Once the title/abstract screening is complete. you will need to copy your included abstracts into a new review, where you will upload PDFs to screen full texts. 


Another option for screening in which you may export search results from citation managers into Excel format. You may want to use multiple spreadsheets to stay organized if using this approach.

Note: All software has the potential to drop some references when importing them into another platform. Check that the number of references you export is the same number you import.

Flow Diagram of Literature Screening

You may choose to include a flow diagram of your excluded and included studies in your review. You can create one using simple tools such as Microsoft Word or PowerPoint. As these examples show, there is more than one way to show your screening process for narrative reviews.