The book: Hua Guofeng's Political Report at the Eleventh National Congress of the Communist Party of China (在中国共产党第十一次 全国代表大会上的 政治报告). The report (and the Congress) officially put an end to the Cultural Revolution and blamed the Gang of Four for its excesses.
The artists' credits also mention Contributed by Jiaonan County Cultural Center (胶南县文化馆供稿).