Update math.mmt

source/math.mmt

@@ -73,7 +73,10 @@ theory NaturalDeduction : ur:?LF =
 
 	/T Natural deduction rules
 
-	 Convention for shorthand notations: {short name of operator/symbol in lower case} {I | R} {- | L | R}
+	 Convention for shorthand notations: {short name of operator/symbol in lower case} {I | E} {ε | L | R}
+	 Here, "I" and "E" stand for either introduction and elimination, respectively. And "ε" (the empty string), "L", "R" hint at the position being either not applicable, left, or right.
+
+
 	 Examples:
 
 	 - "andI" for "and introduction"