If you have trouble locating a dissertation, contact Wayne Shoaf at firstname.lastname@example.org or ph. 213-740-4090 or John Juricek at email@example.com or ph. 213-740-2931.
ProQuest Dissertations & Theses is also a good source for locating digitized dissertations produced at other universities in the United States.
In addition, more and more universities no longer require students to deposit their dissertations with ProQuest so you may want to search for an university's institutional repository via Google and search within that digital collection for a particular publication.