Why People Love Tipping Waiters(popsci.com)
popsci.com
Why People Love Tipping Waiters
http://www.popsci.com/science/article/2013-07/why-do-people-love-tip-waiters
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http://www.popsci.com/science/article/2013-07/why-do-people-love-tip-waiters
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