Citation Order

Citation order means the order in which the elements (building blocks) are combined when a compound number is built. If the classification is used pre-coordinately to organize books on the shelf in a library or create a systematic display on an OPAC, the combination order is pre-determined to ensure consistency.

Generally the citation order for the UDC is:

	Main numbers(s)
	Special auxiliary
	-0 auxiliaries (in reverse numerical order)
	A/Z
	*
	“…”
	(=…)
	(1/9)
	(0…)
	=
	Ex. 624+69+72 Civil engineering, building and architecture
	622”18”(430)=112.2 Mining – 19th century – Germany – text in German