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1. Mementos can no longer be created by specifying a timestamp, and are always created on the current resource state at the current time.
2. Mementos cannot be deleted.

Conditional PUT using If-Match Changes

1. Etags are calculated differently, and can no longer be relied upon for use with the If-Match header for PUT requests.
2. To perform a conditional PUT that works for both Fedora 5 and 6, use X-State-Token with X-If-State-Token instead.