Fix headings in notebook.

doc/notebooks/Pseudo arc-length continuation in the CR3BP.ipynb

@@ -5,8 +5,7 @@
    "id": "cf5bb43b",
    "metadata": {},
    "source": [
-    "Pseudo arc-length continuation in the CR3BP\n",
-    "=====================================\n",
+    "# Pseudo arc-length continuation in the CR3BP\n",
     "\n",
     "In this example we will refine the basic continuation scheme used in [Continuation of Periodic Orbits in the CR3BP](<./Periodic orbits in the CR3BP.ipynb>) and use instead, as continuation parameter, the [pseudo arc-length](https://en.wikipedia.org/wiki/Numerical_continuation#Pseudo-arclength_continuation) to obtain the family of Lyapunov orbits around L1.\n",
     "\n",
@@ -480,7 +479,7 @@
    "id": "a58f836c",
    "metadata": {},
    "source": [
-    "# Corrector\n",
+    "## Corrector\n",
     "We want to find  $\\delta \\underline{\\mathbf y} = [\\delta \\underline{\\mathbf{x}}, \\delta T]$ so that the system of equations (2), reported again below for convenience, is satisfied:\n",
     "$$\n",
     "(2)\n",
@@ -733,7 +732,7 @@
    "id": "fa3b5947",
    "metadata": {},
    "source": [
-    "# Producing the whole Lyapunov family\n",
+    "## Producing the whole Lyapunov family\n",
     "We now use the code produced above to continue to a whole orbit family. We start defining an initial periodic orbit (around L1) and the starting point."
    ]
   },