Untraced reference:

Code b (008/09) indicates that the 100-15X field contains an unestablished heading that is not authorized for use as the lead element in an access point in a bibliographic record.  The heading is not traced as a 4XX See From Tracing field in any other authority record.  The reference record contains a 260 (Complex See Reference) or a 666 (General Explanatory Reference) field to guide the user to established heading(s).

If an unestablished 15X heading may also be used as a subject subdivision,

code g is used in 008/09 when an organization uses one authority record to convey this dual function.

When separate records are created,

code b is used for the untraced reference record, and

code d is used for the subdivision record.

Example:

008/09   b

100  0#  $aDe la

666  ##  $aNames beginning with this prefix are also entered under La (e.g., La Bretèque, Pierre de) or under the name following the prefix (e.g., Torre, Marie de la)