[1] Activity Streams 2.0 (5/21/2017, 2:50:36 PM) <https://w3c.github.io/activitystreams/core/#dfn-link>
[2] Activity Vocabulary (5/21/2017, 2:50:36 PM) <https://w3c.github.io/activitystreams/vocabulary/#dfn-link>
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