The Chinese history books such as "Kanjo" and "Gokanjo" which "Shoki" referred to were usually called 'sho' as a whole including 'ki' in some parts.
『書紀』が参考にした中国史書は、『漢書』『後漢書』のように全体を「書」としその一部に「紀」を持つ体裁をとる。