diff --git a/BLcourse2.3/02_two_dim.py b/BLcourse2.3/02_two_dim.py
index 01bda27d6596781714439a2be7ed8073707505c4..c0c3361717acca16379ed8155a965ac79eca284a 100644
--- a/BLcourse2.3/02_two_dim.py
+++ b/BLcourse2.3/02_two_dim.py
@@ -14,6 +14,15 @@
 # ---
 
 # In this notebook, we use a GP to fit a 2D data set.
+# $\newcommand{\ve}[1]{\mathit{\boldsymbol{#1}}}$
+# $\newcommand{\ma}[1]{\mathbf{#1}}$
+# $\newcommand{\pred}[1]{\rm{#1}}$
+# $\newcommand{\predve}[1]{\mathbf{#1}}$
+# $\newcommand{\test}[1]{#1_*}$
+# $\newcommand{\testtest}[1]{#1_{**}}$
+# $\DeclareMathOperator{\diag}{diag}$
+# $\DeclareMathOperator{\cov}{cov}$
+#
 
 # +
 # ##%matplotlib notebook