When spatial expressions with different semantic roles co-occur, they enter into a relation of hierarchy, and are ordered in the sequence: position (place)-source direction-goal. Their order is chronologically arranged. The positional adverbial appears before other adverbials in accordance with the PTS, since the subject referent must be physically present in a location before he can start from an origin, take a certain direction for his action and to achieve his goal. Being situated in a place, selecting a source for his action, and taking a certain direction all represent states, whose existence precedes the action. Hence the sequential ordering of the adverbials is governed by the PTS. For instance: 他在山坡上从一棵大树后面向山下的游人放冷枪。‘Tā zài shānpō shang cóng yī kē dàshù hòumian xiàng shān xià de yóurén fàng lěngqiāng’ (On the hillside from behind a big tree he fired sniper's shots toward tourists down the hill). An adverbial of position ‘zài + NPloc’ phrase can readily assume the role of a sentential adverbial, appearing in the sentence-initial position. When ordered in front of the sentence, it has the function of creating a ‘scene-setting’, as exemplified by: 在山坡上，他从一棵大树后面向山下的游人放冷枪。‘Zài shānpōshang, tā cóng yī kē dàshù hòumian xiàng shān xià de yóurén fàng lěngqiāng’.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.