牝牡骊黄

Explanation: Li: black. Intent is to observe the nature of things to pay attention, do not care what the appearance, after the analogy of things surface. 　　Usage: Joint type; as object, attribute; metaphor superficial things 　　Source: Song Chenliang "Pan-tert-degree offering text": "Uncle slight degree of independence of its Hin Mu Li Huang and friends of its people, off their joys and sorrows, pity it does not self-contained known to the world."