Subfield $0 contains the system control number of the related authority or classification record, or a standard identifier such as an International Standard Name Identifier (ISNI).  These identifiers may be in the form of text or a Uniform Resource Identifier (URI).  If the identifier is text, the control number or identifier is preceded by the appropriate MARC Organization code (for a related authority record) or the Standard Identifier source code (for a standard identifier scheme), enclosed in parentheses.  When the identifier is given in the form of a Web retrieval protocol, e.g., HTTP URI, no preceding parenthetical is used.

Subfield $0 may contain a URI that identifies a name or label for an entity.  When dereferenced, the URI points to information describing that name.  A URI that directly identifies the entity itself is contained in subfield $1.

See MARC Code List for Organizations for a listing of organization codes and Standard Identifier Source Codes for code systems for standard identifiers.  Subfield $0 is repeatable for different control numbers or identifiers.

Examples:

710  20  $aRoyal Society of Medicine Services (Great Britain)$0(DLC)n##86108151#

511  20  $aCongrès européen de droit rural$0(DLC)n##82111965#

730  #0  $aDead Sea scrolls$0(DLC)n##79071139#

751  #0  $aZimbabwe$0(DLC)n##80089993#

024  7#  $a0000000121491740$2isni

[ISNI for Ruth Rendell]

100  1#  $aRendell, Ruth,$d1930-

500  1#  $aVine, Barbara,$d1930$0(isni)0000000368647620$0http://id.loc.gov/authorities/names/n88276221.html

[ISNI for Barbara Vine] [Barbara Vine is a pseudonym used by Ruth Rendell.]

500  1#  $aYeats, W.B. (William Butler),$d1865-1939$0http://id.loc.gov/authorities/names/n78095579.html$1http://id.loc.gov/rwo/agents/n78095579

To return:

Use the key.

See also:

Appendix A:  Control Subfields