The Copyright Information Office of the University Library has a website with main rules for just use of publications in teaching:

• You can always link (not to illegal content); if necessary create an SFX-link.
• Using Open Access content, such as is available in the Leiden Repository, is always allowed and recommended.
• The use of content from journals for which the university has a license agreement with the publisher is allowed; look at the Terms of use licensed digital resources. The list of licensed publishers does not pertain to book articles.
• Short copies are allowed (if bought through the PRO foundation), if you use citations. The reader agreement defines what a short copy is based on the amount of copied words; images, graphs, tables, overviews, photos, illustration etc. all count towards the maximum (of 200 words). Have a look at the main rules.
• For longer copies you need to apply for permission and payment. You can do this through the PRO foundation portal; have a look at how longer copies without a license and links are to be registered.
• How to digitally publish education materials, has been summarized by the Copyright Information Office.

Regarding all information on copyright and how to use media you can turn to the Copyright Information Office.