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+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ev="http://www.w3.org/2001/xml-events" version="1.1" width="1094.21875" height="793" viewBox="-15 -15 1094.21875 793"><text style="font-family: Verdana; font-size: 12px; font-weight: normal; fill: #000000; line-height: 15px;" transform="translate(684, 15)"><tspan x="0" y="0">1. Trivial Sigma Algebra</tspan><tspan x="0" y="15">2. Element of F  (2 Words)</tspan><tspan x="0" y="30">3. Countable _ are included</tspan><tspan x="0" y="45">4. Infinite _ are included</tspan><tspan x="0" y="60">5. Combination tool for multiple algebras (2 Words)</tspan><tspan x="0" y="75">6. Logical Representation of an Element of the Product Algebra (Abbreviation)</tspan><tspan x="0" y="90">7. Element of Borel Algebra on the reals</tspan><tspan x="0" y="105">8. Property of Constrains in the Product Algebra</tspan><tspan x="0" y="120">9. The opposite of an event</tspan><tspan x="0" y="135">10. Dimension in Machine Learning</tspan><tspan x="0" y="150">11. Other word for Symbolic</tspan><tspan x="0" y="165">12. 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height="35" fill="#d5d5d5" stroke="#000000" stroke-width="1"></rect><text y="23.75" style="line-height: 1; font-family: Verdana; font-size: 16px; font-weight: bold; fill: #ffffff;" x="13.5">2</text></g><g transform="translate(70, 0)"><rect x="0" y="0" width="35" height="35" fill="#d5d5d5" stroke="#000000" stroke-width="1"></rect><text y="23.75" style="line-height: 1; font-family: Verdana; font-size: 16px; font-weight: bold; fill: #ffffff;" x="13.5">3</text></g><g transform="translate(105, 0)"><rect x="0" y="0" width="35" height="35" fill="#d5d5d5" stroke="#000000" stroke-width="1"></rect><text y="23.75" style="line-height: 1; font-family: Verdana; font-size: 16px; font-weight: bold; fill: #ffffff;" x="13.5">4</text></g><g transform="translate(140, 0)"><rect x="0" y="0" width="35" height="35" fill="#d5d5d5" stroke="#000000" stroke-width="1"></rect><text y="23.75" style="line-height: 1; font-family: Verdana; font-size: 16px; font-weight: bold; fill: #ffffff;" x="13.5">5</text></g><g transform="translate(175, 0)"><rect x="0" y="0" width="35" height="35" fill="#d5d5d5" stroke="#000000" stroke-width="1"></rect><text y="23.75" style="line-height: 1; font-family: Verdana; font-size: 16px; font-weight: bold; fill: #ffffff;" x="13.5">6</text></g></g><text transform="translate(0, 763)" style="line-height: 1; font-family: Verdana; font-size: 12px; font-weight: normal; fill: #000000;"><tspan x="0" y="-15">Created with XWords – the free online crossword puzzle generator</tspan><tspan x="0" y="0">https://www.xwords-generator.de/en</tspan></text></svg>
\ No newline at end of file
diff --git a/examples/self_assessment.ipynb b/examples/self_assessment.ipynb
index 0c041bd..807be39 100644
--- a/examples/self_assessment.ipynb
+++ b/examples/self_assessment.ipynb
@@ -4,10 +4,7 @@
    "cell_type": "markdown",
    "id": "511a12a53c44b9d2",
    "metadata": {
-    "collapsed": false,
-    "jupyter": {
-     "outputs_hidden": false
-    }
+    "collapsed": false
    },
    "source": [
     "# Self Assessment Test\n",
@@ -1002,7 +999,7 @@
     "from jupyterquiz import display_quiz\n",
     "\n",
     "q1 = {\n",
-    "       \"question\": \"Which shapes can be represented using the sigma algebra?\",\n",
+    "       \"question\": \"Which shapes can be represented using the product sigma algebra?\",\n",
     "       \"type\": \"many_choice\",\n",
     "         \"answers\": [{\"answer\": \"Triangles\", \"correct\": False},\n",
     "                     {\"answer\": \"Squares\", \"correct\": True},\n",
@@ -1018,6 +1015,18 @@
     "}\n",
     "display_quiz([q1])"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "source": [
+    "Next, solve this crossword puzzle.\n",
+    "\n",
+    "![Crossword Puzzle](../images/crossword_puzzle_sigma_algebra.svg)"
+   ],
+   "metadata": {
+    "collapsed": false
+   },
+   "id": "d0f6cf92e9b8c44a"
   }
  ],
  "metadata": {