《贞观政要·卷九·论安边》
然而，朝廷发兵的时候，黄河以西遇到荒年，田地野草蔓延，几年颗粒未收，十户人家有九户贫困，周边各郡县也都很萧条，五年过去了，还是没有改变。
然则王师初发之岁，河西供役之年，飞刍挽粟，十室九空，数郡萧然，五年不复。
However, when the imperial court sent troops, there was a famine west of the Yellow River, weeds spread over the fields, there was no harvest for several years, nine out of ten families were poor, and the surrounding counties were also depressed. Five years passed, but nothing changed.