A family of Microsoft word processing software products for creating web, email, and print documents.
If you have already cited the source in the document then the Delete option will be greyed out. First delete all the citation from the document and then try to delete from the Source Manager.
To delete the reference in the document, select the citation from the document and click on Delete Once you have deleted all the citations from the document click on References< Manage Sources< highlight the citation from the current list and click Delete.