An article that is perfectly on your topic (or one aspect of it) can be a goldmine (or oyster bed) of information sources. All you need to do is use the references to find other articles, books, and websites that the author felt were important to the topic. You can find the full text of those sources (older than the article you found) by searching the library catalog.
The first step is understanding what type of source each citation points to since this will determine how you search for it. The following tutorials will help you decipher the clues in reference citations if you are unsure.
After you know what type of source each item on the reference list is, you can begin searching the library catalog for the full text.
If you have items that are books or chapters from an edited book or anthology, you want to search the library catalog by the book title.
If you have items that are articles, begin by searching for the article title. If that proves unhelpful, search by the journal name. This will let you know if we have access to the journal and in what format (print or online).
Your perfect article can open a world of other possibilities moving forward as well as backward. Using citation indexes, you can locate other articles that used your perfect article. Many of these new authors will likely discuss your perfect author in ways and for topics that you never dreamed of. Imagine the possiblities this could bring to your dissertation literature review!
Two citation indexes to begin with are Web of Science and Google Scholar. Your goal isn't to find the full text of articles this time, but to identify articles that use your perfect article.