HJØRLAND, Birger. DK5 (Danish Decimal Classification, 5th edition). In: Lifeboat for Knowledge Organization [online]. Last edited 31-03-2006 [cit. 2015-01-20]. Dostupné z: http://www.iva.dk/bh/Lifeboat_KO/SPECIFIC%20SYSTEMS/dk5.htm.
Dostupné z: http://www.iva.dk/bh/Lifeboat_KO/SPECIFIC%20SYSTEMS/dk5.htm.