"You can snort as much cocaine as you want and have as many beautiful women as you want ... but it doesn't make you happy" by Simon Hattenstone, www.theguardian.com. November 23, 2008.
"Punished by Rewards: Twenty-fifth Anniversary Edition: The Trouble with Gold Stars, Incentive Plans, A's, Praise, and Other Bribes". Book by Alfie Kohn, p. 205, 1999.