The cover of the Forbes 400 issue on philanthropy is shown in this handout photo supplied to Reuters September 18, 2012 featuring 12 of the more than 150 influential entrepreneurs the magazine brought together for a private discussion on ways to help solve some of the world�s most intractable problems. From Warren Buffett and Oprah to Bill and Melinda Gates, some of the world�s greatest philanthropists with a combined net worth of $126 billion attended the summit. The Forbes 400 issue goes on sale September 21, 2012. REUTERS/Forbes/Handout
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