“Standing on the shoulders of giants” is how Isaac Newton described his scientific success. Relying on previously published research is how knowledge progresses.
But did you know that study after study shows that articles continue to be cited even after they have been retracted? And that retractions themselves are on the rise? Of course, retractions are not the only kinds of changes that may happen to published documents. There are also corrigenda, errata, protocol updates, enhancements, and withdrawals.
And, multiple sources of content are now available to scholars from the web: from author pages, publisher sites, repositories, and even PDFs from your own hard drive. It can be confusing to decide which version of a paper to trust and to cite.
The CrossMark update identification service from CrossRef will give researchers the information they need to verify they are using the most up-to-date version of a scholarly document.
CrossMark can also provide additional valuable “publication record” information about the content, such as
Readers just click on the CrossMark logo displayed on participating publishers’ HTML and PDF content.

If they are connected to the Internet, they will see a popup box that shows the current status of the document.
Most of the time, a reader will see a message that the document is current like this:

Occasionally, the reader will see a message that the document has updates.

A CrossRef DOI links to the update at the publisher’s site.
This works whether the original document is on the publisher’s site, a third-party site, or viewing a PDF downloaded months earlier.
To see more examples of the CrossMark system, see our Gallery page.
Participating publishers pay for the service, so there is no charge to readers. The articles themselves may be available through a variety of ways, including your institutions’ subscriptions, or they may be openly available, depending on the business model of the publisher.
Any scholarly content that has been assigned a CrossRef DOI may have a CrossMark logo displayed, including
CrossMark logos will only appear on published versions that the publisher has made a commitment to maintain. For this reason, you will not see CrossMark logos on author preprints. CrossMark will be an optional service for CrossRef Member publishers, so not every item with a CrossRef DOI will display a CrossMark logo.
The CrossMark service is not intended to discourage legitimate sharing of published scholarly documents on author home pages or in repositories. It simply provides readers with a way to verify that the articles they rely on have not undergone any material changes since publication.
CrossMark will be particularly useful for readers of open access articles, many of which may be freely shared. The fact that copies of these documents are widely available may make it more difficult for the publisher to communicate in the rare case when a correction or other change materially affects the interpretation of the work. The CrossMark service can help with that communication.
Make a habit of clicking on the CrossMark logo any time you access a document.
It takes only a second, but it can ultimately save an infinite amount of time and trouble.
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