Photo portraits of holocaust survivors in World War II (WWII) are shown during an exhibition named Lest We Forget on the street in Vienna, Austria, May 16, 2019. The photo exhibition, showing portraits shot by photographer Luigi Toscano, kicked off on May 7 and will last to May 31. (Xinhua/Guo Chen)

Photo portraits of holocaust survivors in World War II (WWII) are shown during an exhibition named Lest We Forget on the street in Vienna, Austria, May 16, 2019. The photo exhibition, showing portraits shot by photographer Luigi Toscano, kicked off on May 7 and will last to May 31. (Xinhua/Guo Chen)

People view photo portraits of holocaust survivors in World War II (WWII) during an exhibition named Lest We Forget on the street in Vienna, Austria, May 16, 2019. The photo exhibition, showing portraits shot by photographer Luigi Toscano, kicked off on May 7 and will last to May 31. (Xinhua/Guo Chen)

A citizen views photo portraits of holocaust survivors in World War II (WWII) during an exhibition named Lest We Forget on the street in Vienna, Austria, May 16, 2019. The photo exhibition, showing portraits shot by photographer Luigi Toscano, kicked off on May 7 and will last to May 31. (Xinhua/Guo Chen)

Photo portraits of holocaust survivors in World War II (WWII) are shown during an exhibition named Lest We Forget on the street in Vienna, Austria, May 16, 2019. The photo exhibition, showing portraits shot by photographer Luigi Toscano, kicked off on May 7 and will last to May 31. (Xinhua/Guo Chen)