Skills Earth Sciences

On a roll: Finding similar resources

Searching strategies

Once you have identified the type of literature you are looking for, you can think about the strategy you want to apply during the search. There are three main strategies:

You can use the key words that describe your subject in the search engine. Most engines work with Boolean operators. With this, you can either narrow down or broaden your search with key words.

Boolean Operator Function Example
AND (narrowing down) The engine only gives you results that include the key words connected by the ‘AND’ operator ‘Literature AND Search’
Only hits with Literature and Search are shown
OR (broadening) If you connect two key words with the operator ‘OR’, the engine will give you alle the possible combinations ‘Literature OR Search’

All hits that either contain literature, search or both literature and search are shown

NOT (narrowing down) If you place the operator NOT before a key word, this key word will be excluded in your hits. ‘Literature NOT Search’

Only the hits that contain Literature but not contain Search are shown.

 * (broadening) By truncating a key word with a ‘*’, you are marking the root of your key word. The engine will show you all hits with words based on this root. ‘Inclusi*’

Hits that contain words with the root ‘Inclusi’ will show up. For example, ‘inclusion’, ‘inclusive’, ‘inclusiveness’ etc.

“…“ (narrowing down) With the double quotation marks, the engine only gives you hits with the key words in the exact same combination. “Literature search”

Only hits that have the combination of ‘Literature’ and ‘search’ (with no other words in between) are given.

In addition to these Boolean operators, each search engine has its own filters to further specify your search.

Another strategy is to use the citations from useful sources you already found, and then the citations within these citations, etc. This is called the snowball or chain search. The easiest way to start the search is by finding a very recently published article that is closely related to the subject you are looking at. Most likely, the references within this article contain useful citations for your subject as well. This searching method does not restrict to only finding older publications than the one you started with. Most search engines (i.e. Google Scholar, Scopus) have a ‘cited by’ function. This function allows you to search for publications that cited the article you have in front of you. In this way, you can find more recent publications.

Most search engines have an ‘advanced search’ option. With this option, you can apply more filters to your search than described above. The advanced search option in Scopus is particularly good. Here, not only can you filter with keywords, but for a specific subject area or funding source.

For more information on searching strategies, see 4. Search – Training information skills for Sustainable Development Master in GEO4-2328 – LibGuides at Utrecht University (


Almost all articles published in journals nowadays are available in PDF and books in e-format. However, for these online versions a license is often required to access them. In general, the UU has a license for all major journals, but unfortunately not all.  If there is a UBU-link available for the article or book you are looking for, you know for sure the University guarantees access to this article (UBUlink | Utrecht University ( Another way to check the availability of an article is the Lean Library browser extension that has been developed by the UU. With this extension, you can quickly check if the article you are looking for is available through a UU-license (Online access via Lean Library | Utrecht University (