Closes #11710: create "landing pages" (/library/package.html) for those packages that have no documented content themselves, e.g. "urllib" or "http".
diff --git a/Doc/library/concurrency.rst b/Doc/library/concurrency.rst
index 56fe3f2..fd2dae2 100644
--- a/Doc/library/concurrency.rst
+++ b/Doc/library/concurrency.rst
@@ -15,6 +15,7 @@
 
    threading.rst
    multiprocessing.rst
+   concurrent.rst
    concurrent.futures.rst
    subprocess.rst
    sched.rst