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A marine waits for the arrival of guests before the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. The ceremony will be attended by President Barack Obama and four former presidents. (AP Photo/David J. Phillip) ( Bush Library )

Former president George W. Bush hugs his wife Barbara Bush during the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

Former president Jimmy Carter and his wife, former first lady Rosalynn Carter arrive for the dedication of the George W. Bush Presidential Center, Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

Former British Prime Minister Tony Blair (R) shakes hands in the crowd as he arrives at the dedication for he George W. Bush Presidential Center on the campus of Southern Methodist University in Dallas, Texas April 25, 2013. REUTERS/Mike Stone ( USA-OBAMA/TEXAS )

Former Dallas Cowboys quarterback Troy Aiken, left, arrives during the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

First lady Michelle Obama, U.S. President Barack Obama, former first lady Barbara Bush, former President George H.W. Bush, former President George W. Bush and former first lady Laura Bush attend the opening ceremony of the George W. Bush Presidential Center April 25, 2013 in Dallas, Texas. The Bush library, which is located on the campus of Southern Methodist University, with more than 70 million pages of paper records, 43,000 artifacts, 200 million emails and four million digital photographs, will be opened to the public on May 1, 2013. The library is the 13th presidential library in the National Archives and Records Administration system. (Photo by Alex Wong/Getty Images) ( 167431113 )

Guests wait for a dedication ceremony at the George W. Bush Library and Museum on the grounds of Southern Methodist University on April 25, 2013 in Dallas, Texas. The Bush library is dedicated to chronicling the presidency of the United State's 43rd President. BRENDAN SMIALOWSKI/AFP/Getty Images ( 519212740 )

Former US Secretary of State Colin Powell before a dedication ceremony at the George W. Bush Library and Museum on the grounds of Southern Methodist University April 25, 2013 in Dallas, Texas. The Bush library is dedicated to chronicling the presidency of the United State's 43rd President, George W. Bush. BRENDAN SMIALOWSKI/AFP/Getty Images ( 519214293 )

Former President George W. Bush talks with his father, former President George H. W. Bush, left, during the dedication of the George W. Bush Presidential Center, Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

Former Vice President Dick Cheney, center, shakes hands with former British Prime Minister Tony Blair during the dedication of the George W. Bush presidential library on the campus of Southern Methodist University in Dallas, Thursday, April 25, 2013. Former President George W. Bush's daughter Jenna Bush Hager is at right. (AP Photo/Charles Dharapak) ( Bush Library )

Dallas Cowboys owner and general manager Jerry Jones during the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

Former president William J. Clinton speaks with his wife former first lady Hillary Clinton during the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. At right is former president former president Jimmy Carter. (AP Photo/David J. Phillip) ( Bush Library )

Former US President George H. W. Bush (L), former US President George W. Bush and Laura Bush listen during a dedication ceremony at the George W. Bush Library and Museum on the grounds of Southern Methodist University April 25, 2013 in Dallas, Texas. The Bush library is dedicated to chronicling the presidency of the United State's 43rd President, George W. Bush. BRENDAN SMIALOWSKI/AFP/Getty Images ( 519217234 )

US President Barack Obama (L) and former US Presidents George W. Bush (C) and Bill Clinton arrive on stage for the George W. Bush Presidential Center dedication ceremony in Dallas, Texas, on April 25, 2013. JEWEL SAMAD/AFP/Getty Images ( 519216706 )

US President Barack Obama (L) and former US Presidents (L-R) George W. Bush, Bill Clinton, George H.W. Bush and Jimmy Carter arrive on stage for the George W. Bush Presidential Center dedication ceremony in Dallas, Texas, on April 25, 2013. JEWEL SAMAD/AFP/Getty Images ( 519216895 )

U.S. President Barack Obama (L) applauds as former President George W. Bush arrives on stage at the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013. Bush returns briefly to the U.S. political stage with the dedication of his presidential library on Thursday, an event that will offer Americans a fresh look at his eight storm-tossed years in the White House. REUTERS/Jason Reed ( USA-BUSH/LIBRARY )

US First Lady Michelle Obama (L) and former First Ladies (L-R) Laura Bush, Hillary Clinton, Barbara Bush and Rosalynn Carter arrive on stage to attend the George W. Bush Presidential Center dedication ceremony in Dallas, Texas, on April 25, 2013. JEWEL SAMAD/AFP/Getty Images ( 519217238 )

U.S. First Lady Michelle Obama and President Barack Obama stand alongside members of the Bush family, former first lady Barbara Bush, former presidents George H.W. Bush and George W. Bush and former first lady Laura Bush, as they attend the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013. Obama is in Texas to stand shoulder-to-shoulder with former President George W. Bush in what could serve as a powerful reminder of the ongoing struggle against terrorism, from the Sept. 11 attacks to the Boston Marathon bombings. REUTERS/Jason Reed ( USA-OBAMA/TEXAS )

U.S. President Barack Obama stands alongside former presidents George W. Bush, Bill Clinton, George H.W. Bush and Jimmy Carter as they attend the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013. Obama is in Texas to stand shoulder-to-shoulder with former President George W. Bush in what could serve as a powerful reminder of the ongoing struggle against terrorism, from the Sept. 11 attacks to the Boston Marathon bombings. REUTERS/Jason Reed ( USA-OBAMA/TEXAS )

Former president George W. Bush and his wife Laura Bush listen to former president Jimmy Carter during the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

George W. Bush's daughter Jenna Bush Hager, her husband Henry Hager, sister Barbara Bush, Miky Fabrega, former Governor of Florida Jeb Bush, and his wife Columba Bush attend the opening ceremony of the George W. Bush Presidential Center April 25, 2013 in Dallas, Texas. The Bush library, which is located on the campus of Southern Methodist University, with more than 70 million pages of paper records, 43,000 artifacts, 200 million emails and four million digital photographs, will be opened to the public on May 1, 2013. The library is the 13th presidential library in the National Archives and Records Administration system. (Photo by Alex Wong/Getty Images) ( 167426190 )

U.S. President Barack Obama, former first lady Laura Bush, former President George W. Bush, former President Bill Clinton, former President George H.W. Bush and former President Jimmy Carter attend the opening ceremony of the George W. Bush Presidential Center April 25, 2013 in Dallas, Texas. The Bush library, which is located on the campus of Southern Methodist University, with more than 70 million pages of paper records, 43,000 artifacts, 200 million emails and four million digital photographs, will be opened to the public on May 1, 2013. The library is the 13th presidential library in the National Archives and Records Administration system. (Photo by Kevork Djansezian/Getty Images) ( 167431109 )

Former president George W. Bush, left, shakes hands with former president William J. Clinton during the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

President Barack Obama laughs with former first lady Barbara Bush during the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

President Barack Obama and First Lady Michelle Obama watch as former first lady Barbara Bush gives the thumbs up to guests during the dedication of the George W. Bush Presidential Center Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )

First lady Michelle Obama, former first lady Laura Bush, former first lady Hillary Clinton, former first lady Barbara Bush and former first lady Rosalynn Carter attend the opening ceremony of the George W. Bush Presidential Center April 25, 2013 in Dallas, Texas. The Bush library, which is located on the campus of Southern Methodist University, with more than 70 million pages of paper records, 43,000 artifacts, 200 million emails and four million digital photographs, will be opened to the public on May 1, 2013. The library is the 13th presidential library in the National Archives and Records Administration system. (Photo by Alex Wong/Getty Images) ( 167431621 )

U.S. President Barack Obama speaks during the opening ceremony of the George W. Bush Presidential Center April 25, 2013 in Dallas, Texas. The Bush library, which is located on the campus of Southern Methodist University, with more than 70 million pages of paper records, 43,000 artifacts, 200 million emails and four million digital photographs, will be opened to the public on May 1, 2013. The library is the 13th presidential library in the National Archives and Records Administration system. (Photo by Kevork Djansezian/Getty Images) ( 167431640 )

Former US President George W. Bush and Laura Bush listen while US President Barack Obama speaks during a dedication ceremony at the George W. Bush Library and Museum on the grounds of Southern Methodist University April 25, 2013 in Dallas, Texas. BRENDAN SMIALOWSKI/AFP/Getty Images ( 519217644 )

Former First Lady Laura Bush listens while former US President George W. Bush speaks during a dedication ceremony at the George W. Bush Library and Museum on the grounds of Southern Methodist University April 25, 2013 in Dallas, Texas. The Bush library is dedicated to chronicling the presidency of the United State's 43rd President, George W. Bush. BRENDAN SMIALOWSKI/AFP/Getty Images ( 519217811 )

Former U.S. Secretary of State Condoleezza Rice (L) delivers remarks at the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013. Behind Rice are (L-R) first lady Michelle Obama, President Barack Obama, former first lady Barbara Bush, former President George H.W. Bush, former President George W. Bush and former first lady Laura Bush. REUTERS/Jason Reed ( USA-BUSH/LIBRARY )

Former U.S. presidents George W. Bush (C) and his father George H.W. Bush laugh alongside former first ladies Laura Bush (R) and Barbara Bush (L) during the dedication ceremony for the George W. Bush Presidential Center in Dallas, April 25, 2013. Obama is in Texas to stand shoulder-to-shoulder with former president George W. Bush in what could serve as a powerful reminder of the ongoing struggle against terrorism, from the Sept. 11 attacks to the Boston Marathon bombings. REUTERS/Jason Reed ( USA-OBAMA/TEXAS )

Former U.S. President Jimmy Carter leaves the stage at the end of the dedication of the George W. Bush Presidential Center on the campus of Southern Methodist University in Dallas, Texas April 25, 2013. REUTERS/Mike Stone ( USA-BUSH/LIBRARY )

Former First Lady Laura Bush speaks during a dedication ceremony at the George W. Bush Library and Museum on the grounds of Southern Methodist University April 25, 2013 in Dallas, Texas. The Bush library, which is located on the campus of Southern Methodist University, with more than 70 million pages of paper records, 43,000 artifacts, 200 million emails and four million digital photographs, will be opened to the public on May 1, 2013. BRENDAN SMIALOWSKI/AFP/Getty Images ( 519219461 )

Former Prime Minister of Italy Silvio Berlusconi (C) attends the George W. Bush Presidential Center dedication ceremony in Dallas, Texas, on April 25, 2013. JEWEL SAMAD/AFP/Getty Images ( 519218952 )

Production crews put the finishing touches on the stage before the dedication ceremony of the George W. Bush Presidential Center, Thursday, April 25, 2013, in Dallas. (AP Photo/David J. Phillip) ( Bush Library )