diff --git a/index.yml b/index.yml
index b18a792..f8fd8e8 100644
--- a/index.yml
+++ b/index.yml
@@ -6,13 +6,16 @@
 - lable: HR
   sub:
     - lable: Argief (beta)
+      url: argief
       sidebar:
         # year 1
 
         - WIS10 #empty
         - ELE10 #empty
         - PEE10 #empty
-        - ELE20 #empty
+        - lable: ELE20
+          sub:
+            - opamp
 
         #- WIS20
         - EMS10 #empty