Excerpts from Books and Wikipedia
By May 1957, Mao, stung by criticism, halts hundred Flowers campaign and punishes intellectuals. [Fall and Rise of China Guidebook, Timeline] "Mao Zedong's invitation to Chinese intellectuals to freely air grievances. When complaints turned to attacks on the CCP, Mao launched the Anti-Rightist Rectification movement. [Fall and Rise of China Guidebook, p. 190]