072 SUBJECT CATEGORY CODE (R)
Indicators First Undefined; contains a blank (^) Second Code source 0 National Agricultural Library subject category code list 7 Code source specified in subfield $2
Subfield Codes $a Subject category code (NR) $x Subject category code subdivision (R) $2 Code source (NR) $6 Linkage (NR) $8 Field link and sequence number (R)