Sima Guang
Initially, Sima Guang hired Liu Shu (劉恕) and Zhao Junxi as his main assistants, but Zhao was soon replaced by Liu Ban (劉攽), a Han history expert. In 1070 Emperor Shenzong approved Guang's request to add Fan Zuyu (范祖禹), a Tang history expert. Because "Zizhi tongjian" is a distillation from a large number (322) of disparate historical sources , the selection, drafting, and editing processes used in creating the work as well as potential political biases of Sima Guang, in particular, have been the subject of academic debate.