《元史·列传·卷五十四》
太宗四年，蒙古大军下河南，善向太宗弟拖雷献策，因而任命他为必赤。
岁壬辰，国兵下河南，善以策干太第拖雷，命为必阇赤。
In the fourth year of Taizong, when the Mongol army came to Henan, Shan advised Taizong’s younger brother Tolui, and so was appointed as “Bichi.”