《新唐书·列传·卷一百四十六》
高昌，距京师西有四千多里。幅员横八百里，纵五百里，共有二十一城。
高昌，直京师西四千里而赢，其横八百里，纵五百里，凡二十一城。
Gaochang was over four thousand li west of the capital. It covered an area of eight hundred by five hundred li, and had a total of twenty-one cities.