《资治通鉴·宋纪·宋纪八》
当初，北魏入侵中原时，使用《景初历》。太武帝战胜北凉沮渠氏后，得到赵所著的《玄始历》，当时人们认为很精密。
初，魏入中原，用《景初历》，世祖克沮渠氏，得赵匪攵《玄始历》，时人以为密，是岁，始行之。
At the beginning, when the Northern Wei Dynasty invaded the Central Plains, it used the "Jingchu Calendar". After Emperor Taiwu defeated Juqu clan of Bei Liang, he obtained "Xuan Shi Calendar" written by Zhao, which was considered very precise at that time.