Erwin (Sid) Engst (1918–2003; Chinese: 阳早; pinyin: Yáng Zǎo) was an American advisor to the People's Republic of China.
On August 29, 1966, Hinton, Engst and two other Americans living in China signed a big-character poster with the following text:[citation needed] "Which monsters and freaks are pulling the strings so foreigners get this kind of treatment?
"News of the poster made its way to Mao Zedong, who approved of its contents, remarking in a September 8, 1966 letter to Lin Biao and other leaders that the Americans should indeed be treated equally.
Hinton describes the changes she and Engst had witnessed in China since the beginning of the economic reforms of Deng Xiaoping in the late 1970s.
"[6] Their eldest son, Yang Heping (Fred Engst), moved back to Beijing in 2007 as a professor at the University of International Business and Economics.