To be a document of title a document must purport to be issued by or addressed to a bailee and purport to cover goods in the bailee ' s possession which are either identified or are fungible portions of an identified mass 作为产权文件,其必须由受托人签发且其包含的货物处于受托人的占有之下,该货物可以是特定的也可以是特定量中可替代的部分。