[Air-L] Definitions for Social Media Sites

First of all I have found this group to be an amazing resource. So thank you. Second, I am a criminologist who researches social media, so I am still learning. That said, I am looking for a good and trusted academic resource for definitions for social media sites. It could be a book, or a website, but I am attempting to provide appropriate definitions for reddit, 4chan, YikYak, etc. What is a go-to source for that? Thank you in advance! Best, Becky Rebecca Hayes, Ph.D. Sociology, Anthropology & Social Work Central Michigan University