Subfield $w/0 - Special relationship: [4XX and 5XX: Tracing Fields - Simple Cross References]
Subfield $w/0 contains a one-character alphabetic code that describes a relationship between the heading in a 1XX field and a heading in a 4XX or 5XX field that is more specific than the relationship implicit in the tag. The codes may be used to generate a special reference instruction phrase in a cross reference display.
The codes are:
b - Later heading d - Acronym | g - Broader term h - Narrower term i - Reference instruction phrase in subfield $i n - Not applicable |