diff --git a/src/03-format.ipynb b/src/03-format.ipynb
index cc4abc0..3419a7e 100644
--- a/src/03-format.ipynb
+++ b/src/03-format.ipynb
@@ -504,7 +504,7 @@
    "outputs": [],
    "source": [
     "# Pour chaque valeur, déterminer si non définie\n",
-    "surveys_df.isnull()"
+    "surveys_df.isna()"
    ]
   },
   {
@@ -517,7 +517,7 @@
    "outputs": [],
    "source": [
     "# For each value, is the value undefined\n",
-    "surveys_df.isnull()"
+    "surveys_df.isna()"
    ]
   },
   {
@@ -530,7 +530,7 @@
    "outputs": [],
    "source": [
     "# Sélectionner les enregistrements ayant au moins une valeur NaN\n",
-    "masque_nan = surveys_df.isnull().any(axis='columns')\n",
+    "masque_nan = surveys_df.isna().any(axis='columns')\n",
     "surveys_df[masque_nan]"
    ]
   },
@@ -544,7 +544,7 @@
    "outputs": [],
    "source": [
     "# Select rows with at least one undefined value\n",
-    "nan_mask = surveys_df.isnull().any(axis='columns')\n",
+    "nan_mask = surveys_df.isna().any(axis='columns')\n",
     "surveys_df[nan_mask]"
    ]
   },
@@ -558,7 +558,7 @@
    "outputs": [],
    "source": [
     "# Qu'est-ce que le code suivant va retourner?\n",
-    "une_selection = surveys_df[surveys_df['weight'].isnull()]\n",
+    "une_selection = surveys_df[surveys_df['weight'].isna()]\n",
     "une_selection.groupby('species_id')['record_id'].count()"
    ]
   },
@@ -572,7 +572,7 @@
    "outputs": [],
    "source": [
     "# What does this do?\n",
-    "one_selection = surveys_df[surveys_df['weight'].isnull()]\n",
+    "one_selection = surveys_df[surveys_df['weight'].isna()]\n",
     "one_selection.groupby('species_id')['record_id'].count()"
    ]
   },
@@ -952,8 +952,7 @@
     "        * Méthodes : `astype()`\n",
     "* **Nettoyage**\n",
     "    * `df.copy()`\n",
-    "    * `isna()`, `isnull()` (le second est un alias du premier)\n",
-    "    * `notna()`, `notnull()`  (le second est un alias du premier)\n",
+    "    * `isna()`, `notna()`\n",
     "    * `colonne.fillna(valeur, inplace=True)`\n",
     "* **Sauvegarde**\n",
     "    * `df.to_csv(nom_csv, index=False)`"
@@ -975,8 +974,7 @@
     "        * Method: `astype()`\n",
     "* **Cleaning data**\n",
     "    * `df.copy()`\n",
-    "    * `isna()`, `isnull()` (the second is an alias of the first)\n",
-    "    * `notna()`, `notnull()`  (the second is an alias of the first)\n",
+    "    * `isna()`, `notna()`\n",
     "    * `column.fillna(value, inplace=True)`\n",
     "* **Saving a DataFrame**\n",
     "    * `df.to_csv(csv_filename, index=False)`"