In the library's Volter database, there are plenty of Open Access resources indexed in the search (e.g. DOAJ).
In the Volter search there are, for example, the following Open Access journal resources:
It's also possible to add single OA journals to Volter as required. Suggestions and requests can be sent to firstname.lastname@example.org.
You can also search the following international OA books in Volter:
Single books can be added as needed (e.g. if they are course books or if the authors are from the University of Turku). Please send any suggestions to email@example.com.
Kopernio and Unpaywall in browser (click pictures to see bigger versions)
The Kopernio button appears down on the left and the Unpaywall button on the right side of the page. If a free version is found via Unpaywall, the lock logo is green and "open". The Kopernio button, instead, shows where and in which form the free version is found.
Both buttons can also be found on the tool bar/address bar. Here, the Kopernio search returns the results in Google Scholar. The Unpaywall button only shows if it has access to the current page or not.