would you plz share the materials which shows that coverage mechanism doesn't suit short summary, thx

[zty-work]

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[zty-work]

In the Change part, "The pointer-generator model has two mechanisms, which are copy mechanism and coverage mechanism, I found some materials, they show the Coverage mechanism doesn't suit short summary, so I didn't use this mechanism, just use the first one."
Would you please share the materials which shows that coverage mechanism doesn't suit short summary, maybe blogs or papers, thanks a lot!