Update to new version with fixed references.

index.html

@@ -5,10 +5,10 @@ <h1>Understanding Deep Learning</h1>
 
 <h2> Download draft PDF </h2>
 
-<a href="https://github.com/udlbook/udlbook/releases/download/v0.5.0/UnderstandingDeepLearning_23_01_23_C.pdf">Draft PDF Chapters 1-18</a><br> 2023-01-23. CC-BY-NC-ND license
+<a href="https://github.com/udlbook/udlbook/releases/download/v.0.5.1/UnderstandingDeepLearning_24_01_23_C.pdf">Draft PDF Chapters 1-18</a><br> 2023-01-24. CC-BY-NC-ND license
 <br>
 <ul>
-	<li> Chapters 18-20 (coming soon)
+	<li> Chapters 19-20 (coming soon)
 	<li> Report errata via <a href="https://github.com/udlbook/udlbook/issues">github</a> or contact me directly at [email protected]
 	<li> Follow me on <a href="https://twitter.com/SimonPrinceAI">Twitter</a> or <a href="https://www.linkedin.com/in/simon-prince-615bb9165/">LinkedIn</a> for updates.
 </ul>