540 Subfield $c - Authorization:

Subfield $c contains the source of authority for the restriction (e.g., a specific statute, contract, etc.).

Example:

540 ##$3Bituminous Coal Division and National Bituminous Coal Commission Records$a"No information obtained from a producer disclosing cost of production or sales realization shall be made public without the consent of the producer from whom the same shall have been obtained"; $c50 Stat.88.