Do you want to ask Li Zhengyuan, a professor at Lanzhou University, why he stopped giving lectures? As of August 2, 20231day, this person had not given lectures because he had retired.

According to official website from the College of History and Culture of Lanzhou University, Li Zhengyuan is a researcher and tutor of master students in the Institute of Higher Education of Lanzhou University. Li Zhengyuan was born in 1964 10, and graduated from the Philosophy Department of Lanzhou University in 1986. He is from Baiyin, Gansu. Li Zhengyuan is 59 years old, and Li Zhengyuan has retired, so he doesn't give lectures.