Holocaust Museum at 20

Ilse Feldheim Holocaust survivor Ilse Feldheim, 85, of Great Neck, N.Y., and others wait in a tent across the street from the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013, for the start of a ceremony on the 20th anniversary of the museum. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

Susan Bachrach In this Thursday, April 25, 2013 photo, United States Holocaust Memorial Museum curator Susan Bachrach speaks during a preview of the new exhibit "Some Were Neighbors: Collaboration & Complicity in the Holocaust" at the museum in Washington. The exhibition, opening April 30, 2013, includes interviews with perpetrators of collaboration and complicity in the Nazi genocide. (AP Photo/Carolyn Kaster)

AP Photo/Carolyn Kaster

Holocaust Museum Survivors Return In this Thursday, April 25, 2013 photo, video and imagery are seen during a preview of the new exhibit "Some Were Neighbors: Collaboration & Complicity in the Holocaust" at the United States Holocaust Memorial Museum in Washington. The exhibition, opening April 30, 2013, includes interviews with perpetrators of collaboration and complicity in the Nazi genocide. (AP Photo/Carolyn Kaster)

AP Photo/Carolyn Kaster

US Holocaust Museum Anniversary Audience members including Holocaust survivors, veterans and family members stand during a moment of silence in a tent sent up across from the museum for the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

Elie Wiesel, Bill Clinton Attendees cross the street in the rain to the United States Holocaust Memorial Museum after an event held in a tent marking the 20th anniversary of the museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

Susan Bachrach In this Thursday, April 25, 2013 photo, museum curator Susan Bachrach discusses a group of photographs showing a local Ukrainian auxiliary policeman killing a Jewish woman and child in 1941, during a preview of the new exhibit "Some Were Neighbors: Collaboration & Complicity in the Holocaust" at the United States Holocaust Memorial Museum, in Washington. The exhibition opens April 30, 2013, and is about collaboration and complicity in the Nazi genocide, including interviews with some perpetrators. (AP Photo/Carolyn Kaster)

AP Photo/Carolyn Kaster

Holocaust Museum Survivors Return This Thursday, April 25, 2013 photo shows an armband with the Star of David and a badge for a forced laborer in Germany at the United States Holocaust Memorial Museum during a preview of the new exhibit "Some Were Neighbors: Collaboration & Complicity in the Holocaust" in Washington. The exhibition, opening April 30, 2013, includes interviews with perpetrators of collaboration and complicity in the Nazi genocide. (AP Photo/Carolyn Kaster)

AP Photo/Carolyn Kaster

Ilse Feldheim Holocaust survivor Ilse Feldheim, 85, of Great Neck, N.Y., and others, wait in a tent across the street from the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013, for the start of a ceremony on the 20th anniversary of the United States Holocaust Memorial Museum. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

US Holocaust Museum Anniversary Military honor guard are illuminated by stage lights as they return to retrieve flags on stage at the end of the ceremony for the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

Thomas de Maiziere German Defense Minister Thomas de Maiziere attends the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

US Holocaust Museum Anniversary World War II veterans stand as they are recognized for their service at the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

Bill Clinton Former President Bill Clinton walks backstage after an event marking the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

Scottie Ooton, Bill Clinton, Rebecca Dupas, Elie Wiesel Former President Bill Clinton, right, and poet Rebecca Dupas, left, present Nobel Peace Prize laureate Elie Wiesel, a Holocaust survivor, second from left, and World War II Army veteran Scottie Ooton, a member of the 84th Infantry Division which liberated Hannover-Ahlem concentration camp, second from right, with pins marking the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak

Elie Wiesel Nobel Peace Prize laureate and Holocaust survivor Elie Wiesel speaks at the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

AP Photo/Charles Dharapak