These sites and the descriptions of them are taken from the chapter, "Real world data fluency: How to use raw data" by Wendy Stephens, in the book Creating Data Literate Students, edited by Kristin Fontichiaro, Jo Angela Oehrli, and Amy Lennex. The book was published in 2017.
Citing your sources during your project -- not just at the end -- is an essential habit. Fortunately, citation management tools like NoodleTools make it so easy!