Update UnitSystem.md

wiki/doc/UnitSystem.md

@@ -111,6 +111,12 @@ Description how to build units witht the D-SI format is [here](StructureSIUnits.
 |\zebi|gold|zebi |Zi|1180591620717411303424|[1, p. 143]|
 |\yobi|gold|yobi |Yi|1208925819614629174706176|[1, p. 143]|"
 
+## Operators for combining units
+|D-SI Identifyer|Description|Examples|D-SI Medal |
+|-:|-:|-:|-:|
+| |Multiplication: simply append one unit to another |\metre\metre|PLATINUM|
+|\tothe{n} | Exponent: following a unit where n is an integer or (+-)0.5 |\metre\tothe{2}, \volt\tothe{-0.5}|PLATINUM|
+|\per |Division: All units on the left side of the operator devided by all units on its right side |\metre\per\metre|SILVER|
 
 ### References