Open Educational Resources (OER) are teaching, learning, and research resources that are free of cost and access barriers, and which also carry legal permission for open use. (SPARC)
this permission is granted by use of an open license (for example, Creative Commons licenses) which allows anyone to freely use, adapt and share the resource—anytime, anywhere.
“Open” permissions are defined in terms of the “5R’s”: users are free to Retain, Reuse, Revise, Remix and Redistribute these educational materials.
"5 Keys to Open Textbooks" by GW Libraries can be reused under the CC BY license
