Supplementary searches

In order to make searches as exhaustive as possible, methods other than searching databases can also be used. You can, for example:

• Look in the reference lists of the included studies.
• See how the included studies have been cited by others.
• Identify important journals that you search by hand
• Contact important researchers in the field.

Citation chaining

Citation chaining, sometimes called snowballing, is a search method where you look at the bibliographies of key articles to find other related articles. The articles retrieved this way might not have been retrieved in your database searches, making it a complementary search method. There are two main types of citation chaining, backward chaining and forward chaining.

Backward & forward chaining

• Backward chaining is a good way to find earlier research on your topic. Check the reference lists of key sources, to see which works they have cited.
• Forward chaining is a good way to find more updated research on your topic. Check citations for key sources to see which works that have cited them. This works best for articles that are a few years old, as they are more likely to have been cited than newer ones.

Forward chaining in subject specific databases

Several of the subject specific databases in the list found under "Searching in databases" lets you do forward chaining.

Example from a database record in Criminology collection

Forward chaining in citation databases

The are also citation databases specifically intended for forward chaining, where you can find out how an article has been cited by other researchers.

Example from a database record in Web of Science

Forward chaining in Google Scholar

You can also use Google Scholar to do forward chaining, search for the title and click "Cited by..." to get a list of other articles where the authors have cited the article you're looking at.

Related articles

Another chaining method, is using the database feature "Related articles". The articles featured shares similar features with your key article, so this might be a good way of finding more articles. Several of the the databases from the library shows related articles. The databases uses different names for this feature, for example "Suggested sources", "Related records" and "Similar articles".

Grey literature

In the process of searching for information for a systematic review, you often come into contact with the concept of grey literature. Grey literature refers to studies and texts that have not been published in the usual channels. It can be studies and articles that are ongoing or that were never published, but also Internal documents and reports or dissertations and conference contributions.