Benutzungsbeschränkung; Geheimhaltungsangaben
        engl.: Restrictions on access
   Definition: Lizenzrechtliche oder sicherheitsbezogene Einschränkungen der Benutzung
               
               
               
               
MARC21       355     Security Classification Control (R)
  Subfields: 
             $a   Security classification
             $b   Handling instructions (R)
             $c   External dissemination information (R)
             $d   Downgrading or declassification data
             $e   Classification system [NEW]
             $f   Country of origin code
             $6   Linkage

 Indic/etc.: 1st: Controlled element
             0 Document
             1 Title
             2 Abstract
             3 Contents note
             4 Author
             8 Other element
             2nd: Undefined; contains a blank (#)
             
MARC21       506     Restrictions on Access Note (R)
  Subfields: 
             $a   Terms governing access
             $b   Jurisdiction (R)
             $c   Physical access provisions (R)
             $d   Authorized users (R)
             $e   Authorization (R)
             $u   Uniform Resource Identifier
             $3   Materials specified
             $5   Institution to which field applies
             $6   Linkage