edited layout files

The layout files were edited in such a way that "Source: original work" now links to a Wiki page explaining what that means.

Author: JoramSoch

404.html

@@ -24,7 +24,6 @@ <h1>This page doesn't exist!</h1>
 
 <div class="list">
   <ul>
-    <li>If the URL reads <code class="language-plaintext highlighter-rouge">.../Proofs/[shortcut].html</code>, try to call <code class="language-plaintext highlighter-rouge">.../P/[shortcut]</code>.</li>
 	<li>If the URL reads <code class="language-plaintext highlighter-rouge">.../P/[shortcut]</code>, create a <a href="/contribute/">new page</a> using the <a href="https://raw.githubusercontent.com/StatProofBook/StatProofBook.github.io/master/P/-temp-.md">proof template</a>.</li>
     <li>If the URL reads <code class="language-plaintext highlighter-rouge">.../D/[shortcut]</code>, create a <a href="/contribute/">new page</a> using the <a href="https://raw.githubusercontent.com/StatProofBook/StatProofBook.github.io/master/D/-temp-.md">definition template</a>.</li>
   </ul>

_layouts/definition.html

@@ -31,7 +31,7 @@ <h1 class="post-title">Definition: {{ page.title }}</h1>
 	    </li>
 	  {% endfor %} </ul><br>
 	{% else %}
-	  <b>Sources:</b> <br><ul><li>original work</li></ul><br>
+	  <b>Sources:</b> <br><ul><li><a href="https://github.com/StatProofBook/StatProofBook.github.io/wiki/What-does-%22original-work%22-mean%3F">original work</a></li></ul><br>
     {% endif %}
 
 	<!-- Metadata -->

_layouts/proof.html

@@ -31,7 +31,7 @@ <h1 class="post-title">Proof: {{ page.title }}</h1>
 	    </li>
 	  {% endfor %} </ul><br>
 	{% else %}
-	  <b>Sources:</b> <br><ul><li>original work</li></ul><br>
+	  <b>Sources:</b> <br><ul><li><a href="https://github.com/StatProofBook/StatProofBook.github.io/wiki/What-does-%22original-work%22-mean%3F">original work</a></li></ul><br>
     {% endif %}
 
 	<!-- Metadata -->