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編目園地僅答覆資訊組織相關問題，您提問之問題，建議您可以直接參考原文內容中的說明（第52頁)。

原文網址：https://ia800405.us.archive.org/10/items/crewmethod12/crewmethod12.pdf

Is the copyright date for e-books included in the calculation of the collection's average copyright age? Older material that is no longer useful should be culled. Keep in mind that the release date for an e-book is not always the same as the copyright date. Some third party vendors can't readily provide the copyright date unless that information was provided by the original producer of the electronic item so you may need to do some research. 

編目園地敬覆 107.1.2