They studied books about classical Chinese medicine.

他们研究了有关中医的书籍。

However, despite the years of built up experience among translators, the work is still made difficult due to the complicated nature, long history and large volume of classical Chinese literature.

然而，尽管翻译家们已经积累了多年的经验，可由于中国古典文学的性质复杂、历史悠久、体量庞大，这项工作仍然很困难。

The five works are rooted in Chinese classics, involving heroic figures such as Zhao Yun, Guan Yu and Zhang Fei from The Romance of Three Kingdoms, one of the four great classical Chinese novels.

五部作品均植根于中国经典，涉及赵云、关羽、张飞等英雄人物的《三国志》，中国四大名著之一。

Besides, he was very active in the popularization of classical Chinese literature in the West.