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Chinese actors perform the musical "Green Path and Rainbow - the Story of Flying Tigers and the Hump" at the opening ceremony of the 4th Sino-American Second World War Friendship and Flying Tiger History Conference in Las Vegas, the United States, May 10, 2019. The 4th Sino-American Second World War Friendship and Flying Tiger History Conference opened here Friday to commemorate the American and Chinese heroes and the U.S.-China cooperation during World War II (WWII). (Xinhua/Han Fang)