A documentary film recording the voices of survivors and witnesses who experienced the Nanjing Massacre 78 years ago is shown during a mourning activity held at the Chinese Culture Center of San Francisco in California, the United States, Dec. 12, 2015. More than 300 people attended an activity held in the Chinese Culture Center of San Francisco on Sunday to mark the death of victims in Nanjing Massacre from Dec. 13, 1937 to January 1938. (Xinhua/Liu Yilin)