When using images, sound or video found online, one should be careful and aware that copyright still applies. Just because it is available online it does not mean you can take it and use it – check the license.
There are various types of licenses that inform you how that item can be used. Creative Commons, “a nonprofit organization that helps overcome legal obstacles to the sharing of knowledge and creativity to address the world’s most pressing challenges”, has done a very good job at informing the public about the most common types of licensing. Not only is each type of license, identified by their respective logo, described briefly, the license deed and legal code are also made available. Thus one can quickly see what they can do with the material, under what circumstances.
Attribution 4.0 International (CC BY 4.0)
Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0)
Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Another possibility is to create a references handout; this is especially recommended if you have more than just a few references that would make a slide look too busy.
How do I properly credit the author? Recommended practices for attribution from Creative Commons.
The Nova Southeastern University Office of Copyright is attached to the Alvin Sherman Library, Research, and Information Technology Center and is intended to be the central resource for all matters concerning copyright.
It provides training in the form of live seminars and webcasts about the policy and the proper use of copyrights at the University.
The Office of Copyright can also advise graduate and undergraduate students with respect to copyright issues.