Neglected Food Bubbles: The Espresso Coffee Foam User qznc_bot, in the Hacker News subreddit, 13 Sep 2016
Neglected Food Bubbles: The Espresso Coffee Foam User dabshitty, in the Everything Science subreddit, 13 Sep 2016
Everything You Always Wanted to Know About Espresso Crema* (*But Were Afraid to Ask) User cheekygeek, in the Coffee subreddit, 12 Sep 2016
For all of you espresso-loving science buffs: a scientific study of crema by the food chemist, Ernesto Illy. User phonedump, in the Coffee subreddit, 04 Feb 2013