code: def to_most_recent_reference
        me = DeepClone.clone(self)
        me.disable_id_attribute
        @relations << DocumentRelation.new(type: "instance", identifier: nil, url: nil, bibitem: me)
        @abstract = []
        @dates = []
        @docidentifier.each(&:remove_date)
      end
docs: convert ISO:yyyy reference to reference to most recent
   instance of reference, removing date-specific infomration:
   date of publication, abstracts. Make dated reference Instance relation
   of the redacated document