US First Lady Michelle Obama, former US President Jimmy Carter, US President Barack Obama and former US President Clinton arrive at the Lincoln Memorial on the National Mall August 28, 2013 in Washington, DC. Obama and others spoke to commemorate the 50th anniversary of the US civil rights era March on Washington where Martin Luther King Jr. delivered his “I Have a Dream Speech”. AFP PHOTO/Brendan SMIALOWSKI (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)