 Complete the following phrase:  Premier Zhou Enlai, a widely respected senior CCP leader, died on January 8, 1976. On April 5, at the Qingming Festival, thousands of Beijings residents gathered in Tiamen Square. They wrote poems and put up big character posters in Tiamen Square to mourn for Zhou and express their anger towards the impious Gang of Four and the destructive Cultural Revolution. In response, Mao ordered the police and the PLA to disperse the people, and around four thousand were arrested. This incident was also called the 