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Numerical Subfields
$8 Language Code
A three letter code from the MARC Code List for languages (ISO 639-2)1) that indicated the language of the subfield $a or $n following immediately.
$9 Cataloguer's Note
Any data or annotation to the field's content that should not be displayed publicly. In practice this subfield will be used to temporarily store record ids that need to be mapped into CT ids or any markers or flags relating to the field in question. Notes with a more permanent character and those intended to be read by other cataloguers should be given in field 830 instead.