U.S. President Barack Obama walks with a letter before he departs the Oval Office for the final time as sitting president, at the White House in Washington, U.S. January 20, 2017. In keeping with presidential tradition, President Obama slipped a letter into the desk in the Oval Office for President-elect Donald Trump — on Thursday the letter that George W. Bush wrote to him was released by Bush, as well as the letter that Bill Clinton wrote to Mr. Bush, each on the last day of his presidency.