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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. In the 3rd-century AD, the Chinese scholar Du Yu interpolated the "Zuo Zhuan" with the "Annals" so that each entry of the "Annals" was followed by the corresponding passages of the "Zuo Zhuan". Du Yu's version of the text was the basis for the "Right Meaning of the "Annals"" ( ) which became the imperially authorised text and commentary on the "Annals" in 653 AD. Modern scholars disagree about whether the "Zuo Zhuan" 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".