Author, A. A. (Year). Data set name [Data file]. Retrieved from URL
Pew Research Center. (2013, May 1). Home internet access [Data file]. Retrieved from http://www.pewresearch.org/data-trend/media-and-technology/internet-pene...
In-text: (Pew Research Center, 2013)
Include the type of data set (e.g. Data file, Code book) in square brackets after the title.