diff --git a/Lecture9.ipynb b/Lecture9.ipynb
index 22fea52..f464d84 100644
--- a/Lecture9.ipynb
+++ b/Lecture9.ipynb
@@ -13,7 +13,7 @@
    "source": [
     "```{admonition} Margaret Atwood\n",
     ":class: tip\n",
-    "Every aspect of human technology has a dark side, including the bow and arrow\n",
+    "Every aspect of human technology has a dark side, including the bow and arrow.\n",
     "```"
    ]
   },
diff --git a/slides/MLforMaterials_Lecture9_Challenge.pdf b/slides/MLforMaterials_Lecture9_Challenge.pdf
index 6738f81..d8b5c3b 100644
Binary files a/slides/MLforMaterials_Lecture9_Challenge.pdf and b/slides/MLforMaterials_Lecture9_Challenge.pdf differ