URI
Notation
+
Caption
Coordination. Addition (plus sign). Table 1a
Scope Note
The coordination sign + (plus) connects two or more separated (non-consecutive, non-related) UDC numbers, to denote a compound subject for which no single number exists
Examples
(44+460) France and Spain
(470+571) Russia. Russian federation
622+669 Mining and Metallurgy
Broader class
--  COMMON AUXILIARY SIGNS