Add dummy_threading to toctree.
diff --git a/Doc/library/someos.rst b/Doc/library/someos.rst
index 02e29ec..8140270 100644
--- a/Doc/library/someos.rst
+++ b/Doc/library/someos.rst
@@ -15,6 +15,7 @@
 
    select.rst
    threading.rst
+   dummy_threading.rst
    _thread.rst
    _dummy_thread.rst
    multiprocessing.rst