UC Library Search allows you to limit your search to newspapers or dissertations, although the results will not be comprehensive. Use the limiters in the left margin after you run your initial search.
You can also go directly to specific newspapers; the library has access to the full run -- from their first issue to today -- of the New York Times, the Washington Post, the Los Angeles Times, the Wall Street Journal, and the Chicago Tribune. You can find all of these listed by name in the A-Z list of article databases. See the News Sources guide for a list of other U.S. and foreign newspapers.
ProQuest Dissertations & Theses database is the most comprehensive list of dissertations published in the U.S. You may want to use the "All Subjects or Indexing - SUBJECT" dropdown menu to avoid picking up irrelevant items.