2. What sources of evidence are there?

2.3. Primary sources

3.3 Primary sources

When would it make sense to search the primary sources?

If no secondary evidence exists in an evidence summary or systematic review, then it might be helpful to search the primary sources. Searching the primary sources is essential for those creating an evidence synthesis themselves.

"Veterinary practitioners may believe that there is not enough time to search for science-based information while managing cases, but these perceptions often change after experiencing the effect this new-found knowledge has on treatment response by the patient.” (Gibbons and Mayer, 2009)

The EBVM methodology developed when scientific research studies were published online, and when sophisticated search tools made focused searching possible.

Bibliographic databases

Bibliographic databases are search tools designed to help you search across the research literature (journal articles, books, conference papers, etc.).

They can focus on a particular subject area or be interdisciplinary. Each database systematically indexes articles from a given list of journals and other scholarly and professional publications, and so provides the most effective and efficient means for searching the scientific literature.

Each database searches a different set of journals and publications, but they are explicit about their coverage and you can check to see what is included.

It should be remembered that databases are tools to identify relevant papers. While some databases contain full-text articles, many do not, and so you will also need to find ways to access the papers you wish to read; how to do so is covered later in this section


If you don’t have access to subscription databases then you can refer directly to the journals that you do have access to, acknowledging that you will not be retrieving the broad spectrum of evidence.