Five former United States presidents walk to the opening ceremony of former President Richard Nixon's library in Yorba Linda, California in this July 19, 1990 file photo. From left to right are: former Presidents George Bush, Ronald Reagan, Jimmy Carter, Gerald Ford, and Richard Nixon. Ford, who took office from an embattled Nixon, has died, according to a statement from his widow on December 26, 2006. REUTERS/Gary Cameron/Files (UNITED STATES)