diff --git a/docs/phoneme_model.md b/docs/phoneme_model.md
index 16155f9d..226303cb 100644
--- a/docs/phoneme_model.md
+++ b/docs/phoneme_model.md
@@ -5,6 +5,9 @@
   - [Initiator](#initiator)
   - [Target](#target)
   - [Manner](#manner)
+- [Place of Articulation](#place-of-articulation)
+  - [Active Articulators](#active-articulators)
+  - [Passive Articulators](#passive-articulators)
 - [Phonation](#phonation)
   - [Voice](#voice)
 - [Vowel Height](#vowel-height)