657 INDEX TERM--FUNCTION (R)
Indicators First Undefined; contains a blank (#) Second Source of term 7 Source specified in subfield $2
Subfield Codes $a Function (NR) $v Form subdivision (NR) $x General subdivision (R) $y Chronological subdivision (R) $z Geographic subdivision (R) $2 Source of term (NR) $3 Materials specified (NR) $6 Linkage (NR)