Sometimes you'll be citing sources that, when cited in the text, look like they are from the same article.
For example, if you have two articles written in 2013 - one written by Harris, Smith, Carlyle and Jones and the other written by Harris, Kumar, Venkman, and Knorr, both will be shortened to (Harris et al., 2013) in the text.
When you've got multiple references written in the same year that shorten to the same name, add as many names as you need in the text to differentiate them from one another. See the link below from the APA website for an example of how to do this.
