Two entries with the same id
If multiple atom:entry elements with the same atom:id value appear in an Atom Feed Document, they represent the same entry. Their atom: updated timestamps SHOULD be different. If an Atom Feed Document contains multiple entries with the same atom:id, Atom Processors MAY choose to display all of them or some subset of them. One typical behavior would be to display only the entry with the latest atom: updated timestamp.
Ensure that these atom:entry elements represent the same entry. This check is not something that can be automated.
If the atom:entry elements in question represent the same entry, be aware that the potential exists that different consumers will display different subsets. If this is not a concern, then no action is necessary. Otherwise, ensure that every distinct entry has a distinct id, and ensure that every unique entry only appears in a given feed exactly once.
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