053 LC CLASSIFICATION NUMBER (R)Indicators First Undefined; contains a blank (^) Second Source of classification number 0 Assigned by LC 4 Assigned by agency other than LC ^ Undefined [OBSOLETE]Subfield Codes $a Classification number element--single number or beginning number of span (NR) $b Classification number element--ending number of span (NR) $c Explanatory term (NR) $5 Institution to which field applies (R) $6 Linkage (NR) $8 Field link and sequence number (R)