Update sympy.ipynb

Author: Tom-van-Woudenberg

book/08/sympy.ipynb

@@ -43,10 +43,10 @@
    "source": [
     "# SymPy\n",
     "\n",
-    "```{sidebar} Information\n",
+    "```{sidebar} Author and external content\n",
     "Written by Tom van Woudenberg\n",
     "\n",
-    "This page reuses CC BY content from {cite:t}`sympy`. {fa}`quote-left`{ref}`Find out more here.<link to external resources section on credits and license page>`\n",
+    "This page reuses CC BY content from {cite:t}`sympy`. {fa}`quote-left`[Find out more here](external_resources)`\n",
     "```\n",
     "\n",
     "SymPy is a Python library for symbolic mathematics. You can use it as a tool to evaluate basic and complicated math operations, whenever they become tedious or error prone.\n",
@@ -1515,14 +1515,6 @@
     "## Gotchas\n",
     "Trial and error is an approach for many programmers, but you may want to prevent frequently made mistakes. Take a look at SymPy's documentation on [gotchas](https://docs.sympy.org/latest/tutorials/intro-tutorial/gotchas.html) to accelerate your learning!"
    ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "## References\n",
-    "```{bibliography}"
-   ]
   }
  ],
  "metadata": {