diff --git a/HP48_notes.txt b/HP48_notes.txt
index b555740..72d8892 100644
--- a/HP48_notes.txt
+++ b/HP48_notes.txt
@@ -5,7 +5,7 @@ Z transform, first define Z as 'EXP(-(0,1)).
 
 i.e.
 
-> 'EXP(-(0,1))'
+> 'EXP(X*(0,-1))'
 > 'Z'
 > STO