When did Yang Lihua and Xu Xiunian start working together

1991. New Di Qing, also known as Di Qing Takes the Flag, is a historical and biographical television opera directed by Chinese Taiwanese director Xu Shengyu and Yang Lihua, written by Tsai Tianshe, Gui Haipeng and Huang Shishen, and starring Yang Lihua, Xu Xiunian, Chen Yalan, Sima Yujiao, Qing Rong, and Ji Liru, which was premiered in 1991, making it the first time Yang Lihua and Xu Xiunian worked together.