Question: When did Li Chengqian's mother die?
Sentence (from "Empress Zhangsun"): Empress Zhangsun (長孫皇后, personal name 長孫無垢) (15 March 601 – 28 July 636), formally Empress Wendeshunsheng (文德順聖皇后, literally "the civil, virtuous, serene, and holy empress") or, in short, Empress Wende (文德皇后), was a Chinese essayist and empress of the Chinese dynasty Tang Dynasty.
Relevant evidence: Yes