If you have read a relevant article on your topic, it is a good idea to go through the reference list to find more sources of interest. The reference list contains all the sources the author has used in the article. In the reference list, you will find material published prior to the article you are starting from.
You can also do a citation search to find which publications have cited to the original article. This way you can find research published after the publication of your original article. By using a citation database such as Scopus or Web of science you can find sources citing to the article you have read. This allows you to follow up on what has happened since the article was published. It gives you the opportunity to follow the discussion and arguments or see how an idea has developed. You can also use Google scholar to find sources that refer to a specific article. Keep in mind that not everything on Google Scholar is scientific.
In this film you can learn more about citation searching. The film has captions.