MARC21       008v'12  General retention policy
     Values: 
              0   Unknown
              1   Other general retention policy
              2   Retained except as replaced by updates
              3   Sample issue retained
              4   Retained until replaced by microform
              5   Retained until replaced by cumulation, replacement
                  volume, or revision
              6   Retained for a limited period
              7   Not retained
              8   Permanently retained