There are several ways of being notified whether a particular article has been cited. Some of the journal databases, such as HEIN, have this feature. However, the most comprehensive, and easist, way is to find the article in Google Scholar and set up an alert.
Search for the title of the article in Google Scholar, and then click on the 'cited by' link.
Scroll to the bottom of the page of citing articles and click 'create alert'. You will be asked for your email address - as citing articles are added to Google Scholar, you will be notified by email.
Another great feature of Google Scholar alerts is that you can click on the 'source it at Melbourne' button next to each citing article to be taken to the University of Melbourne subscription.