/BAKFID=backlink-file-id

    Use this qualifier to look for a file with a specific backlink.
    Only the first part of the file id must be specified, that is,
    if the File id is (x,y,z) one must specifiy 'x' as the file-id.
    Use this qualifier to get files from a specific directory.
    If /BAKFID=0 is used, DFU returns files not belonging to a
    directory (often temporary files).