Be aware that some instructors may have additional or specialized requirements for your citations.
Always be cognizant of class requirements and seek confirmation from classmates or your instructor.
To go along with their popular website, Purdue has created these video tutorials to demonstrate formatting an APA paper and creating a reference list.
At the library, when we have a question about how to cite we check out Purdue's Online Writing Lab website. It is excellent!
DOIs (Digital Object Identifiers) attempt to provide stable URLs to online materials such as journal articles. APA recommends providing the DOI when available in the reference list.