bpo-33649: Add low-level APIs index. (GH-9364)

diff --git a/Doc/library/asyncio-subprocess.rst b/Doc/library/asyncio-subprocess.rst
index ef8a1cb..57a7a37 100644
--- a/Doc/library/asyncio-subprocess.rst
+++ b/Doc/library/asyncio-subprocess.rst
@@ -318,6 +318,8 @@
 control a subprocess and the :class:`StreamReader` class to read from
 the *stdout*.
 
+.. _asyncio_example_create_subprocess_exec:
+
 The subprocess is created by the :func:`create_subprocess_exec`
 function::
 
@@ -349,5 +351,5 @@
     print(f"Current date: {date}")
 
 
-See also the :ref:`same example <asyncio-subprocess-proto-example>`
+See also the :ref:`same example <asyncio_example_subprocess_proto>`
 written using low-level APIs.