The source of the heading in the 7XX field may be specified using either second indicator value “7” with subfield $2 or a second indicator value that specifies the source. For access points coming from the LC/NAF file, prefer the second indicator with the value "0". | The source of the heading in the 7XX field may be specified using either second indicator value “7” with subfield $2 or a second indicator value that specifies the source. For access points coming from the LC/NAF file, prefer the second indicator with the value "0". |