352 DIGITAL GRAPHIC REPRESENTATION (R)Indicators - Both undefined; each contains a blank (^)Subfield Codes $a Direct reference method (NR) $b Object type (R) $c Object count (R) $d Row count (NR) $e Column count (NR) $f Vertical count (NR) $g VPF topology level (NR) $i Indirect reference description (NR) $6 Linkage (NR) $8 Field link and sequence number (R)