The American Psychological Association (APA) Style citation format is widely used in the sciences and social sciences. Here are the best starting points for working with the APA Style:
DOI stands for digital object identifier. This set of characters allows users to find any electronic format source using a simple DOI resolver app.
The DOI for Barbara van Schewick's article looks like this:
APA Style requires that you include a DOI at the end of every citation for those materials that have been assigned this identifier. You can find a DOI either on the top or bottom of the first page of the source you are citing, or by using the DOI finding utility.
Here is the sample reference for the article you have to review:
van Schewick, B. (2009). Point Counterpoint: Network Neutrality Nuances.
Communications of the ACM, 52(2), 31-34. doi: 10.1145/1461928.1461942