Former U.S. President Bill Clinton looks at former U.S. President George W. Bush (L) as he speaks during a moderated conversation at the graduation of the inaugural class of the Presidential Leadership Scholars program, a partnership between the presidential centers of George W. Bush, William J. Clinton, George H.W. Bush, and Lyndon B. Johnson at the George W. Bush Presidential Library in Dallas, Texas July 9, 2015. REUTERS/Mike Stone