There are several other excellent online guides to using copyrighted materials in your dissertation, and considering post-publication issues such as the value of publishing open access and when to choose an embargo.
Kenneth D. Crews, Copyright and Your Dissertation or Thesis: Ownership, Fair Use, and Your Rights and Responsibilities
University of Michigan's Copyright for Dissertations: Getting Started
University of Michigan's A Graduate Student's Guide to Copyright: Open Access, Fair Use, and Permissions (from 2010)
Hillary Corbett, ETDs and the Consequences of Openness
Ohio State's Copyright in Your Thesis or Dissertation
If your particular question isn't addressed here, there's a good chance that U.S. Copyright Office's Compendium has something to say about whether that type of resource is copyrightable, and the level of protection it receives.
Compendium of U.S. Copyright Office Practices, Third Edition (2014)
Download full text of the Compendium (1,288 pages).
The Table of Contents is here.