Frankly, this is something that already should be, and to a large degree is, manually checked by editors and referees.
While this is a problem that should be taken seriously, it’s also something that mainly affects trash-tier journals. You won’t find many hallucinated citations in Nature or Science (I doubt there has been a single one), and authors have strong incentives to prevent it from happening as they risk their reputation (and with it future grants).
Then machine checking should be implemented
Whatever needs to be restructured to make citations automatically verifiable needs to happen, and then this will be less of an issue.
Frankly, this is something that already should be, and to a large degree is, manually checked by editors and referees.
While this is a problem that should be taken seriously, it’s also something that mainly affects trash-tier journals. You won’t find many hallucinated citations in Nature or Science (I doubt there has been a single one), and authors have strong incentives to prevent it from happening as they risk their reputation (and with it future grants).