Instructors using Turnitin Feedback Studio can include the following statement in their syllabi.

University of Missouri has a license agreement with Turnitin.com, a service that helps detect plagiarism by comparing student papers with Turnitin's database and Internet sources. Students who take this course agree that all required papers may be submitted to Turnitin.com. Students who submit papers to Turnitin retain the copyright to the work they created. 

A copy of submitted papers is retained in a Turnitin database archive to be compared with future submissions—a practice that helps protect and strengthen copyright ownership. Use of the Turnitin service is subject to the Terms and Conditions of Use posted on Turnitin's website at http://turnitin.com/en_us/about-us/privacy/legal-faqs.