510 CITATION/REFERENCES NOTE (R)
Indicators First Coverage/location in source 0 Coverage unknown 1 Coverage complete 2 Coverage is selective 3 Location in source not given 4 Location in source given Second Undefined; contains a blank (^)
Subfield Codes $a Name of source (NR) $b Dates of coverage of source (NR) $c Location within source (NR) $x International Standard Serial Number (NR) $3 Materials specified (NR) $6 Linkage (NR) $8 Field link and sequence number (R)