APA reference list example: Supplemental material published only online. The author is listed by last name and initial: Samuel, T. The date is listed by year, month and day in parentheses, followed by a period: (2009, March 27). The article title is Mind the wage gap followed by no punctuation. The label is in brackets followed by a period: [Supplemental material]. The journal title is italicized, followed by a period: The American Prospect. The words “Retrieved from” are followed by the URL, with no period at the end: http://www.prospect.org/