Wikipedia:Published

This page is the summary of much discussion on policy talk pages. It is not a guideline, but rather an effort to clarify the definition of the words "published" and "accessible" as used on guideline and policy pages.

The term published is most commonly associated with text materials, either in traditional printed format or online. However, audio, video, and multimedia materials that have been recorded then broadcast, distributed, or archived by a reputable party may also meet the necessary criteria to be considered reliable source. Like text sources, media sources must be normally produced by a reliable third party and be properly cited. Additionally, an archived copy of the media must exist and be available to the general public. It is useful but by no means necessary for the archived copy to be accessible via the Internet.

"The source is available to the public to review in some manner."

The idea behind requiring a source to be 'accessible' is to allow a third-party, unaffiliated, person to review the source. This is a requirement of WP:V. The third party is someone who is unaffiliated with the editor, publisher, group or institution in control of the source, or primary source of the information or expression (such as art). This third party must have some possibility of being able to verify that the source exists and contains the information purported.

However the mere fact that an item is no longer available online, without cost, or in a retail store is insufficient to nullify its "accessible" status. If the item is available online or at a library, it is still "accessible".

...
Wikipedia