code: def references(self, key, value):
      
      def _has_curator_flag(value):
          normalized_nine_values = [el.upper() for el in force_list(value.get('9'))]
          return 'CURATOR' in normalized_nine_values
  
      def _is_curated(value):
          return force_single_element(value.get('z')) == '1' and _has_curator_flag(value)
  
      def _set_record(el):
          recid = maybe_int(el)
          record = get_record_ref(recid, 'literature')
          rb.set_record(record)
  
      rb = ReferenceBuilder()
      mapping = [
          ('0', _set_record),
          ('a', rb.add_uid),
          ('b', rb.add_uid),
          ('c', rb.add_collaboration),
          ('e', partial(rb.add_author, role='ed.')),
          ('h', rb.add_refextract_authors_str),
          ('i', rb.add_uid),
          ('k', rb.set_texkey),
          ('m', rb.add_misc),
          ('o', rb.set_label),
          ('p', rb.set_publisher),
          ('q', rb.add_parent_title),
          ('r', rb.add_report_number),
          ('s', rb.set_pubnote),
          ('t', rb.add_title),
          ('x', rb.add_raw_reference),
          ('y', rb.set_year),
      ]
  
      for field, method in mapping:
          for el in force_list(value.get(field)):
              if el:
                  method(el)
  
      for el in dedupe_list(force_list(value.get('u'))):
          if el:
              rb.add_url(el)
  
      if _is_curated(value):
          rb.curate()
  
      if _has_curator_flag(value):
          rb.obj['legacy_curated'] = True
  
      return rb.obj
docs: Populate the ``references`` key.