Duplication recognition

hadaxu

It would be nice if there is a feature that helps me not to create another article if it already there (or bring up some warning that the article is already in the library).

ajlyon

Yes, it would be nice. See http://forums.zotero.org/discussion/42 for the first discussion of this, a good 15,600 discussions threads ago. It hasn't happened yet, but there's no doubt that this is a known issue, and everyone is hoping that it will be resolved eventually.