delete category tag

How do I delete a category tag from a reference?

If that category is still

If that category is still available, you can select those references, and click the "Categorize..." button. Select the category and click the Remove button. For a single reference, you can check off that category on the reference editor. If that category is already deleted, you can select references and go to "Edit | Replace". Limit the replace operation to field "Categories". For a single reference, you can just select that category in the Categories field and delete it.