diff --git a/doc/source/models/cubics.ipynb b/doc/source/models/cubics.ipynb
index 1b1ba08af73bfbb8d92bbffbd7af4dca1954e601..616e1b37239eae973b1b2158d07d8c90cffd1a7e 100644
--- a/doc/source/models/cubics.ipynb
+++ b/doc/source/models/cubics.ipynb
@@ -37,7 +37,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 2,
    "id": "9a884dab",
    "metadata": {},
    "outputs": [],
@@ -68,17 +68,17 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 3,
    "id": "a8c87890",
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "<teqp.teqp.GenericCubic at 0x20b222799b0>"
+       "<teqp.teqp.GenericCubic at 0x18f604c3a70>"
       ]
      },
-     "execution_count": 7,
+     "execution_count": 3,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -89,6 +89,39 @@
     "teqp.canonical_PR(Tc_K, pc_Pa, acentric, kmat)\n",
     "teqp.canonical_SRK(Tc_K, pc_Pa, acentric, kmat)"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "c3a62795",
+   "metadata": {},
+   "source": [
+    "## Superancillary\n",
+    "\n",
+    "The superancillary equation gives the co-existing liquid and vapor (orthobaric) densities as a function of temperature. The set of Chebyshev expansions was developed in https://pubs.acs.org/doi/abs/10.1021/acs.iecr.1c00847 .  These superancillary equations are more accurate than iterative calculations in double precision arithmetic and also at least 10 times faster to calculate, and cannot fail in iterative routines, even extremely close to the critical point. \n",
+    "\n",
+    "The superancillary equation is only exposed for pure fluids to remove ambiguity when considering mixtures.  The returned tuple is the liquid and vapor densities"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "id": "1b02ef72",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(30846.392909514052, 42.480231719002326)"
+      ]
+     },
+     "execution_count": 7,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "teqp.canonical_PR([Tc_K[0]], [pc_Pa[0]], [acentric[0]]).superanc_rhoLV(100)"
+   ]
   }
  ],
  "metadata": {