A citation for a consulted source in which information is found about the 1XX heading in an
established heading record. The information found in the source may also be present.
Each additional source of information is recorded in a separate 670 note.
$a - Source citation (NR)
In UNBIS, the entire note is recorded in subfield $a.
670 $a AGROVOC
670 $a Unesco thesaurus
670 $a Documents of Conference of European Statisticians
670 $a A/CN.9/527
670 $a Security Council agenda item S/58 
670 $a List of descriptors in transport economics
670 $a Scope note from Transportation Logistics dictionary