diff --git a/exercizes/notebooks/Installation process.ipynb b/exercizes/notebooks/Installation process.ipynb
index de8bd7cc..0923bcf9 100644
--- a/exercizes/notebooks/Installation process.ipynb	
+++ b/exercizes/notebooks/Installation process.ipynb	
@@ -1,5 +1,5 @@
 {
- "cells": [
+  "cells": [
   {
    "cell_type": "markdown",
    "metadata": {},
diff --git a/exercizes/notebooks/ex_0_joint_space_inverse_dynamics_arm.ipynb b/exercizes/notebooks/ex_0_joint_space_inverse_dynamics_arm.ipynb
index 1e1642e7..04eee69d 100644
--- a/exercizes/notebooks/ex_0_joint_space_inverse_dynamics_arm.ipynb
+++ b/exercizes/notebooks/ex_0_joint_space_inverse_dynamics_arm.ipynb
@@ -1,5 +1,5 @@
 {
- "cells": [
+  "cells": [
   {
    "cell_type": "markdown",
    "metadata": {},
diff --git a/exercizes/notebooks/ex_1_com_sin_track_talos.ipynb b/exercizes/notebooks/ex_1_com_sin_track_talos.ipynb
index a5e1f8c4..1d707a61 100644
--- a/exercizes/notebooks/ex_1_com_sin_track_talos.ipynb
+++ b/exercizes/notebooks/ex_1_com_sin_track_talos.ipynb
@@ -1,5 +1,5 @@
 {
- "cells": [
+  "cells": [
   {
    "cell_type": "markdown",
    "metadata": {},
diff --git a/exercizes/notebooks/ex_3_biped_balance_with_gui.ipynb b/exercizes/notebooks/ex_3_biped_balance_with_gui.ipynb
index f6db703c..c63fad6d 100644
--- a/exercizes/notebooks/ex_3_biped_balance_with_gui.ipynb
+++ b/exercizes/notebooks/ex_3_biped_balance_with_gui.ipynb
@@ -1,5 +1,5 @@
 {
- "cells": [
+  "cells": [
   {
    "cell_type": "code",
    "execution_count": null,