Sources

https://arstechnica.com/gadgets/2013/06/ux-spotlight-behind-the-scenes-of-tumblrs-design-process/

http://fortune.com/2017/11/27/tumblr-david-karp-leaving/

https://nypost.com/2017/11/27/tumblr-ceo-david-karp-is-stepping-down/

https://www.gartner.com/en/research/methodologies/gartner-hype-cycle

https://www.statista.com/statistics/246214/share-of-us-internet-users-who-use-tumblr-by-age-group/

https://www.businessinsider.com/tumblr-and-social-media-demographics-2013-12

https://www.theringer.com/tech/2017/11/29/16713354/david-karp-tumblr