All Creative Commons licenses require that authors/creators be recognized. The only exception to this is those resources that are in the public domain. Resources that are in the public domain may bear the license CC0 (CC zero) to indicate this status. While many openly licensed resources may request and not require attribution, providing a proper attribution is a recognized best practice.
ASCCC OERI Attribution Guide
ASCCC OER Licensing and Attributions (Creative Commons) Webinar Resources
How to Build Open Attributions – simple steps for properly attributing a resource.
Creative Commons – Choose a License – “This chooser helps you determine which Creative Commons License is right for you in a few easy steps.”
Open Washington’s Open Attribution Builder – “This is a tool to help you build attributions. Click the About box to learn more. As you fill out the form, the app automatically generates the attribution for you.”