Once you have found some relevant or important articles on your topic, one way to expand your search is through citation searching.  Citation searching looks for all of the articles or books that have cited your initial paper since it was written.  There are two main databases you can use for this kind of search:  Web of Science and Google Scholar.  Both of these databases cover somewhat different sources, so it can be helpful to try both.

Web of Science Cited Reference Search

Select the Cited References tab. Next, search by either the author's name or the article title. 

Find the entry that matches the article you had in mind. Click on the number of citing articles to view the articles that cited the initial work.

Google Scholar Cited Reference Search: