OER – Educational resources (including textbooks) created with an open copyright license, as opposed to the traditional all-rights reserved model of copyright licensing. OER learning materials are free to copy, use, adapt and re-share.
Look for the CC-BY- license reference.
This means you can revise and customize OERs to suit your classroom needs and outcomes.
More information, including suggestions about where to look for OERs, is available on the NSCC OER Guide.