The Commentary of Zuo, also known as the Zuo Zhuan, composed in the early 4th century BC, is a general history covering the period from 722 to 468 BC which follows the succession of the rulers of the State of Lu. Modern scholars disagree about whether it is truly a commentary on the Spring and Autumn Annals or an independent work. In any case, scholars have found it by far the most useful among the three surviving 'commentaries' both as a historical source for the period and as a guide to interpreting the Annals.