More accurate header for course links

staging/index.html

@@ -45,7 +45,7 @@
 <div class="project">
 <h2>Use in classes</h2>
 
-<h3>Classes where CPDT is/was the primary text</h3>
+<h3>Classes where CPDT is/was a primary text</h3>
 <ul>
 <li>EECS 755 at U. Kansas <a href="http://perry.alexander.name/eecs755/">(Fall 2017)</a></li>
 <li>CS691PL at U. Mass. Amherst <a href="https://www.cs.umass.edu/~arjun/courses/cs691pl-spring2014/">(Spring 2014)</a></li>