《汉书·志·律历志上》
吕是用来集中天阳以发出气息，一叫做林钟，二叫做南吕，三叫做应钟，四叫做大吕，五叫做夹钟，六叫做中吕。
吕以旅阳宣气，一曰林钟，二曰南吕，三曰应钟，四曰大吕，五曰夹钟，六曰中吕。
The lv are used to concentrate celestial yang and emit breath. They are: one called Linzhong, two called Nanlv, three called Yingzhong, four called Dalv, five called Jiazhong, and six called Zhonglv.