The system is able to identify two or more references as duplicates. Duplicates have a quite common occurrence even within a single set of results from one source of references. Another moment when you benefit from deduplication is, when you run a search on the same topic in multiple different databases, but in your final result list, you naturally want to have each reference only once.

Duplicate removal is the reason why the numbers of references in resources and in Preview can differ.

1. Duplicates which are identified by ID (meaning they are from the same database) are removed automatically, so only one reference is displayed in Preview.
2. Other duplicates are identified by a combination of different criteria. You can set these criteria in the project settings:

ID (cannot be disabled)

In case of identical ID, only one reference is displayed in Preview.

DOI

Identifying duplicates based on the article's DOI.

URL

Identifying duplicates based on the article's URL.

Source/Vol/Year/Page

Identifying duplicates based on the journal's name, volume, publication year and start page of the article.

Title/Page

Identifying duplicates based on the title and start page of the article.

Title/Authors/Year/Page

Identifying duplicates based on the title, authors, publication year and start page of the article.

When the active rules apply to two or more articles (e.g. have the same title and start page), then the articles are evaluated as duplicates. Only the first one is displayed in the result list and the others are assigned to it. Such records are marked with an icon showing the number of duplicates. If, however, you discover that there are no duplicates, you can turn the duplicate into a standard record by clicking the Not duplicate button.

If the duplicate also contains an abstract or DOI, it will be automatically used to complete the record.

<aside> 💡 For a quick overview of duplicates, use the Has filter in the left menu, where records with duplicates (from point 2 above) are listed.

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