556 Subfield $a - Information about documentation note:

Subfield $a contains the text of the documentation note.

Examples:

556 ##$a1970 censuses of population file (A, B, or C) summary tape (sample). Arlington, Va. : Data use and Access Laboratories, 1972. (Technical document ; no. ST-4P).

556 ##$aBASIC reference. 3rd ed. Boca Raton, Fl. : IBM, c1984. (Personal computer hardware reference library); 6361132.