diff --git a/doc/LectureNotes/_build/.doctrees/environment.pickle b/doc/LectureNotes/_build/.doctrees/environment.pickle
index 92992074d..0ffddc3a5 100644
Binary files a/doc/LectureNotes/_build/.doctrees/environment.pickle and b/doc/LectureNotes/_build/.doctrees/environment.pickle differ
diff --git a/doc/LectureNotes/_build/.doctrees/exercisesweek37.doctree b/doc/LectureNotes/_build/.doctrees/exercisesweek37.doctree
index 6fb5ac1d6..4c2740d63 100644
Binary files a/doc/LectureNotes/_build/.doctrees/exercisesweek37.doctree and b/doc/LectureNotes/_build/.doctrees/exercisesweek37.doctree differ
diff --git a/doc/LectureNotes/_build/html/_sources/exercisesweek37.ipynb b/doc/LectureNotes/_build/html/_sources/exercisesweek37.ipynb
index 3ae3ea9e9..c565e7b07 100644
--- a/doc/LectureNotes/_build/html/_sources/exercisesweek37.ipynb
+++ b/doc/LectureNotes/_build/html/_sources/exercisesweek37.ipynb
@@ -2,7 +2,7 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "id": "ebfc874e",
+   "id": "cfebae03",
    "metadata": {
     "editable": true
    },
@@ -14,7 +14,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "8ecf95b0",
+   "id": "353ebb07",
    "metadata": {
     "editable": true
    },
@@ -27,7 +27,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "7940e437",
+   "id": "c02815dd",
    "metadata": {
     "editable": true
    },
@@ -45,7 +45,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "964cf4c4",
+   "id": "fb152043",
    "metadata": {
     "editable": true
    },
@@ -57,7 +57,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "bc8b093a",
+   "id": "9aba7a46",
    "metadata": {
     "editable": true
    },
@@ -68,7 +68,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "bc1907b5",
+   "id": "be52c097",
    "metadata": {
     "editable": true
    },
@@ -80,7 +80,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "c7d29897",
+   "id": "c54979e5",
    "metadata": {
     "editable": true
    },
@@ -90,7 +90,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "e45dbe57",
+   "id": "4b1eb811",
    "metadata": {
     "editable": true
    },
@@ -102,7 +102,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "0331d3dd",
+   "id": "036a5440",
    "metadata": {
     "editable": true
    },
@@ -114,7 +114,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "51159839",
+   "id": "f7fb8094",
    "metadata": {
     "editable": true
    },
@@ -125,7 +125,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "6df6ca33",
+   "id": "d7d92995",
    "metadata": {
     "editable": true
    },
@@ -137,7 +137,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "6bf812e3",
+   "id": "29eb9701",
    "metadata": {
     "editable": true
    },
@@ -150,7 +150,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "1e04714b",
+   "id": "aa106511",
    "metadata": {
     "editable": true
    },
@@ -162,17 +162,17 @@
   },
   {
    "cell_type": "markdown",
-   "id": "621afaa2",
+   "id": "58be1091",
    "metadata": {
     "editable": true
    },
    "source": [
-    "Show finally that the variance of $\\boldsymbol{\\beta}$ is"
+    "Show finally that the variance of $\\boldsymbol{\\boldsymbol{\\beta}}$ is"
    ]
   },
   {
    "cell_type": "markdown",
-   "id": "b7aa535d",
+   "id": "4cb58e41",
    "metadata": {
     "editable": true
    },
@@ -184,7 +184,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "45ea3a92",
+   "id": "a04df28d",
    "metadata": {
     "editable": true
    },
@@ -195,7 +195,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "3851ded2",
+   "id": "c095c96a",
    "metadata": {
     "editable": true
    },
@@ -207,7 +207,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "c759e617",
+   "id": "5d425a79",
    "metadata": {
     "editable": true
    },
@@ -220,7 +220,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "c16482df",
+   "id": "fb89cfab",
    "metadata": {
     "editable": true
    },
@@ -233,7 +233,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "2e2cda9b",
+   "id": "aea8801c",
    "metadata": {
     "editable": true
    },
@@ -245,7 +245,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "d69a45ab",
+   "id": "0e885693",
    "metadata": {
     "editable": true
    },
diff --git a/doc/LectureNotes/_build/html/exercisesweek37.html b/doc/LectureNotes/_build/html/exercisesweek37.html
index af72df66c..e9f863c97 100644
--- a/doc/LectureNotes/_build/html/exercisesweek37.html
+++ b/doc/LectureNotes/_build/html/exercisesweek37.html
@@ -475,7 +475,7 @@ mean value <span class="math notranslate nohighlight">\(\boldsymbol{X}\boldsymbo
 \[
 \mathbb{E}(\boldsymbol{\hat{\beta}}) = \boldsymbol{\beta}.
 \]</div>
-<p>Show finally that the variance of <span class="math notranslate nohighlight">\(\boldsymbol{\beta}\)</span> is</p>
+<p>Show finally that the variance of <span class="math notranslate nohighlight">\(\boldsymbol{\boldsymbol{\beta}}\)</span> is</p>
 <div class="math notranslate nohighlight">
 \[
 \mbox{Var}(\boldsymbol{\hat{\beta}}) = \sigma^2 \, (\mathbf{X}^{T} \mathbf{X})^{-1}.
diff --git a/doc/LectureNotes/_build/jupyter_execute/exercisesweek37.ipynb b/doc/LectureNotes/_build/jupyter_execute/exercisesweek37.ipynb
index f5cfe5ddf..cc9e06cfc 100644
--- a/doc/LectureNotes/_build/jupyter_execute/exercisesweek37.ipynb
+++ b/doc/LectureNotes/_build/jupyter_execute/exercisesweek37.ipynb
@@ -2,7 +2,7 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "id": "ebfc874e",
+   "id": "cfebae03",
    "metadata": {
     "editable": true
    },
@@ -14,7 +14,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "8ecf95b0",
+   "id": "353ebb07",
    "metadata": {
     "editable": true
    },
@@ -27,7 +27,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "7940e437",
+   "id": "c02815dd",
    "metadata": {
     "editable": true
    },
@@ -45,7 +45,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "964cf4c4",
+   "id": "fb152043",
    "metadata": {
     "editable": true
    },
@@ -57,7 +57,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "bc8b093a",
+   "id": "9aba7a46",
    "metadata": {
     "editable": true
    },
@@ -68,7 +68,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "bc1907b5",
+   "id": "be52c097",
    "metadata": {
     "editable": true
    },
@@ -80,7 +80,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "c7d29897",
+   "id": "c54979e5",
    "metadata": {
     "editable": true
    },
@@ -90,7 +90,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "e45dbe57",
+   "id": "4b1eb811",
    "metadata": {
     "editable": true
    },
@@ -102,7 +102,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "0331d3dd",
+   "id": "036a5440",
    "metadata": {
     "editable": true
    },
@@ -114,7 +114,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "51159839",
+   "id": "f7fb8094",
    "metadata": {
     "editable": true
    },
@@ -125,7 +125,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "6df6ca33",
+   "id": "d7d92995",
    "metadata": {
     "editable": true
    },
@@ -137,7 +137,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "6bf812e3",
+   "id": "29eb9701",
    "metadata": {
     "editable": true
    },
@@ -150,7 +150,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "1e04714b",
+   "id": "aa106511",
    "metadata": {
     "editable": true
    },
@@ -162,17 +162,17 @@
   },
   {
    "cell_type": "markdown",
-   "id": "621afaa2",
+   "id": "58be1091",
    "metadata": {
     "editable": true
    },
    "source": [
-    "Show finally that the variance of $\\boldsymbol{\\beta}$ is"
+    "Show finally that the variance of $\\boldsymbol{\\boldsymbol{\\beta}}$ is"
    ]
   },
   {
    "cell_type": "markdown",
-   "id": "b7aa535d",
+   "id": "4cb58e41",
    "metadata": {
     "editable": true
    },
@@ -184,7 +184,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "45ea3a92",
+   "id": "a04df28d",
    "metadata": {
     "editable": true
    },
@@ -195,7 +195,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "3851ded2",
+   "id": "c095c96a",
    "metadata": {
     "editable": true
    },
@@ -207,7 +207,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "c759e617",
+   "id": "5d425a79",
    "metadata": {
     "editable": true
    },
@@ -220,7 +220,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "c16482df",
+   "id": "fb89cfab",
    "metadata": {
     "editable": true
    },
@@ -233,7 +233,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "2e2cda9b",
+   "id": "aea8801c",
    "metadata": {
     "editable": true
    },
@@ -245,7 +245,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "d69a45ab",
+   "id": "0e885693",
    "metadata": {
     "editable": true
    },