Yunhai jingyuan

Although the Yunhai jingyuan is a lost work, several later dictionaries, such as the (1711) Peiwen Yunfu, followed its system of collating entries by the tone and rime of the last character in a term.

Compared with two contemporary 100-volume dictionaries, the Guiyuan zhucong 桂苑珠叢 by Zhuge Ying 諸葛潁 (539–615) and the 100-volume Zihai 字海 compiled under the direction of Empress Wu Zetian (r. 690–705), the Yunhai jingyuan was an "even more miraculous lexicographical work".

They included several of his literary friends, the Daoist poet Zhang Zhihe, the Chan Buddhist monk Jiaoran 皎然, and Lu Yu, author of The Classic of Tea.

Yan Zhengqing's reference work included not only single-syllable words but also multi-character compounds, and even some chengyu "set phrases".

This type of specialized dictionary was intended for the composition of poems, retrieving literary quotations, and finding appropriate words for antithetical couplets.