Subfield $1 contains a URI that identifies a description of an entity, sometimes referred to as a Thing, a Real World Object or RWO, whether actual or conceptual.  When dereferenced, the URI points to a description of that entity.  A URI that identifies a name or label for an entity is contained in $0.


500  1#  $aGoings, Mary Seach (Mary E.),$d1916-2015$0$1

374  ##  $aAstronauts$0$1$2lcsh

380  ##  $aHorror films$0$1$2lcgft

To return:

Use the key.

See also:

Appendix A:  Control Subfields