diff --git a/AERO3220_HW4_block_diagram.md b/AERO3220_HW4_block_diagram.md
index 6aa14fb..a041cfb 100644
--- a/AERO3220_HW4_block_diagram.md
+++ b/AERO3220_HW4_block_diagram.md
@@ -83,21 +83,21 @@ This version shows the same coupled dynamics using gain blocks and integrator tr
 ```mermaid
 flowchart LR
     Z1[State z1] --> G11[Gain -k1/m1]
-    G11 --> S1[Sum z1ddot]
+    G11 --> S1[Sum z̈₁]
     Z2[State z2] --> G12[Gain +k1/m1]
     G12 --> S1
     S1 --> I11[Transfer block 1/s]
-    I11 --> Z1D[State z1dot]
+    I11 --> Z1D[State ż₁]
     Z1D --> I12[Transfer block 1/s]
     I12 --> Z1
 
     U[Input force u] --> G2U[Gain 1/m2]
-    G2U --> S2[Sum z2ddot]
+    G2U --> S2[Sum z̈₂]
     Z1 --> G21[Gain k1/m2]
     G21 --> S2
     Z2 --> G22["Gain -(k1 + k2)/m2"]
     G22 --> S2
-    Z2D[State z2dot] --> G23[Gain -b/m2]
+    Z2D[State ż₂] --> G23[Gain -b/m2]
     G23 --> S2
     S2 --> I21[Transfer block 1/s]
     I21 --> Z2D