《六韬·豹韬·分险》
太公答道： 当我军部队占领山的左侧时，应迅速戒备山的右侧；占领了山的右侧时，应迅速戒备山的左侧。
太公曰； 处山之左，急备山之右；处山右，急备山左。
Taigong replied: When our army occupies the left side of the mountain, it should quickly be on guard against the right side of the mountain; when it occupies the right side of the mountain, it should quickly be on guard against the left side of the mountain.