The MARC format is quite richer than metadata format Dublin Core and CERIF data format. But the need to fill several very special “library” fields containing bibliographic nuances in universal systems containing scientific information is questionable. It seems that in MARC21 several duplicity data entry in the same record is necessary (i.e. see figure 1, fields 100,700 on the one side and 245$c on the other side). In Dublin core the duplicity data entry of citation appears in different records. In each record the citation have to be added. The data format CERIF allows uniqueness. Every data are entered only once.