《南史·列传·卷七十九》
与邻国有什么外交活动，就让邻国胡人用胡文书写，羊皮作纸。
与旁国通，则使旁国胡爲胡书，羊皮爲纸。
With neighboring countries, there are some diplomatic activities, where 胡人 of the neighboring countries use 胡文 to write and use sheepskin as paper.