537 Source of Data Note (CF) [obsolete]:

Field 537 was made obsolete in 1993. The first indicator was defined as Display constant controller [# (blank ) = No information provided, 8 = No display constant generated]. The second indicator was undefined. The subfield codes were: $a (Source of data note), $6 (Linkage). Source of data information may be contained in field 500 (General Note) or included in field 567 (Methodology Note) .