《宋书·志·卷十六》
天子出征时，向上帝祭祀，推论前时所祭祀过的返回后一定要为之举行告至之礼，那么就应该举行郊祭，不容再有怀疑。
天子出征，类于上帝，推前所告者归必告至，则宜告郊，不复容疑。
When the Son of Heaven went on an expedition, he offered sacrifices to the Lord, and when he considered the declaration on returning from previous sacrifice that he must sacrifice at his suburban altar, he certainly must have done so, with no room for doubt.