續5/7之提問，著錄於856$x是否也可以?與9xx相較，哪一種著錄方式較推薦使用呢?

856 - Electronic Location and Access (R)
$x - Nonpublic note
Note relating to the electronic location of the source identified in the field. The note is written in a form that is not adequate or intended for public display. It may also contain processing information about the file at the location specified.

舉例：
85640$u....$z....$x原書下架換書補償
85640$u....$z....$x原平台為ＯＯＯＯ