Statue debout Bodhisattva Peinture Or Analyse scientifique Collection publique Xi’an chutu liang zun Bei Zhou hanbaiyu guanshi yin xiang wusun fenxi 西安出土两尊北周汉白玉观世音像无损分析 = Non-destructive Analysis and related issues of the White Marble Bodhisattva Statues Dating to the Northern Zhou Stored at Xi’an Museum