《资治通鉴·唐纪·唐纪三十四》
房赶到后，玄宗就问张均、张兄弟的情况，房说： 我约他们一起来追随陛下，而他们却犹豫不决，看他们的意思，好像有什么难言之隐。 
及琯至，上问均兄弟，对曰： 臣帅与偕来，逗留不进：观其意，似有所蓄而不能言也。 
After Fang arrived, Emperor Xuanzong asked him about Zhang Jun and Zhang Duo. Fang said, "I asked them to come and follow Your Majesty, but they hesitated. From their expressions, it seems that they have something they cannot say."