After conducting a fair use evaluation, you may have determined that your use of a copyrighted work requires permission. At this point, it's necessary to figure out who is, in fact, the copyright holder of that work if it's not readily identifiable. Often a publisher website will provide a form or information about how to request permission to reuse content for which they hold the copyright. The Copyright Clearance Center may represent the interests of a copyright holder, in which case you can search for the title or author of a work directly in their website. More in-depth research may require exploring registration records maintained by the U.S. Copyright Office or compiled by other institutions.
The following resources offer starting points for this research; however, you may also contact your subject librarian or the Scholarly Communication Coordinator should you need assistance.