When full text searching fails, or for papers that have not been digitized, a newspaper index can be an invaluable help in locating coverage of interest:
Google News Archive
Google's News Archive drew heavily on Proquest Historical Newspapers, but there was some material that is not in Proquest. Coverage is best for the 20th century United States. It also included some newspapers formerly in the Paper of Record collection. As of Summer 2011, Google stopped adding to or enhancing the News Archive. The News Archive search page has been redirected to the Google News search page. However, it is possible to use the Advanced Search page to limit your results to the Archive content. For a list of all Google News papers, see http://news.google.com/newspapers. For some good advice on searching, see http://searchresearch1.blogspot.com/2013/11/a-note-about-searching-google-scanned.html.