Subfield $w/0-h - Narrower term:  [4XX and 5XX:  Tracing Fields - Simple Cross References]

Code h indicates that the heading in the 4XX or 5XX field is a narrower term than the heading in the 1XX field.  The code may be used to generate a special reference instruction phrase such as search also under the broader term: in a cross reference display.

Example:

150  ##  $aFoot

550  ##  $wh$aToes

Cross reference display example:

Toes

search also under the broader term:  Foot