National Library of Medicine (NLM) catalogers take into account headings and usage in the NLM bibliographic and authority files when preparing new AACR headings.  They also change AACR headings already formulated by LC when the NLM files support a different heading.  For headings used by NLM, the NLM heading has precedence over the LC heading when:

1.   The LC heading has not yet been coded for AACR2, and the NLM heading has already been established as AACR2.

2.   The LC heading has been coded as AACR2-compatible (Descriptive cataloging rules fixed field 008/10 = d) and NLM has established the heading as "pure" AACR2 (Descriptive cataloging rules fixed field 008/10 = c).

3.   Both libraries have headings already coded as "pure" AACR2 and NLM has a greater number of bibliographic records in support of its heading than LC has in support of its heading.  (If the number is equal, the better heading is chosen, basing the decision on judgment.)


670 ## $a NLM files, [date viewed] $b (hdg.: [data]; usage: [data])

670 ## $a NLM/LC files, [date viewed] $b (hdg.: [data]; usage: [data])

Full NLM Record:

040 ## $a DNLM $c DLC $d DLC

100 1# $a Fuller, R.

400 1# $w nnaa a Fuller, Roy, $d 1933-

400 1# $a Fuller, Roy

670 ## $a Probiotics, c1992: $b t.p. (Roy Fuller) list of contrib. p. (Fuller, R., Intestinal Microecology Consultant, Russet House, Ryeish Green, Three Mile Cross, Reading, UK)

670 ## $a LC database, Jan. 29, 1992 $b (hdg.: Fuller, Roy, 1933- ; usage: R. Fuller)

670 ## $a NLM files, Jan. 29, 1992 $b (hdg.: Fuller, R.; usage: R. Fuller, Roy Fuller)

[NLM AACR2 heading has precedence over LC heading.]

See also:

Section II:  Additions and Changes to Authority Records