2 sentences

1. 正文开始前有一篇很长的序言。

   zhèng​wén kāi​shǐ qián yǒu yī piān hěn cháng de xù​yán.

   There is a long preface before the main text begins.

   Source: Dong Chinese Dictionary

2. 这篇序言可以作为理解这本哲学著作内容的引导。

   zhè piān xù​yán kě​yǐ zuò​wéi lǐ​jiě zhè běn zhé​xué zhù​zuò nèi​róng de yǐn​dǎo.

   This preface serves as a guide to understanding the contents of this philosophical work.

   Source: Dong Chinese Dictionary