diff --git a/_doc/notebooks/td1a/td1a_correction_session7.ipynb b/_doc/notebooks/td1a/td1a_correction_session7.ipynb
index d9041747d..ffc4cfce9 100644
--- a/_doc/notebooks/td1a/td1a_correction_session7.ipynb
+++ b/_doc/notebooks/td1a/td1a_correction_session7.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:e64b310e31bebc4faeffeaa18dcda016b2ebe89572b63945f40f168378102c19"
+  "signature": "sha256:133dc16341ba8fd1372e997574f38fd1de0ae45a6670f5b4f4fb4aab2dfd50ca"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -395,7 +395,7 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "``$$ \\xymatrix{  & m-1  & m \\\\      n-1   &  p(n-1,m-1) \\ar[dr]^{ + \\abs{t_n - s_m}} &  p(n-1,m) \\\\      n     &  p(n,m-1)   \\ar[r] & p(n,m) \\\\ \t\t\t\t} $$``"
+      "`` \\xymatrix{  & m-1  & m \\\\      n-1   &  p(n-1,m-1) \\ar[dr]^{ + \\abs{t_n - s_m}} &  p(n-1,m) \\\\      n     &  p(n,m-1)   \\ar[r] & p(n,m) \\\\ \t\t\t\t} ``"
      ]
     },
     {