Question: What is the date of death of Empress Ma (Jianwen)'s husband?
Sentence (from "Jianwen Emperor"): Some people speculated that one of the reasons behind why the Yongle Emperor sponsored the admiral Zheng He on his treasure voyages in the early 15th century, was for Zheng He to search for the Jianwen Emperor, who was believed to have survived and fled to Southeast Asia.
Relevant evidence: No