Bug #1464658: make clear that PyList_GetItem doesn't take negative indices.
diff --git a/Doc/api/concrete.tex b/Doc/api/concrete.tex
index 3a918be..98e0e03 100644
--- a/Doc/api/concrete.tex
+++ b/Doc/api/concrete.tex
@@ -1803,8 +1803,9 @@
\begin{cfuncdesc}{PyObject*}{PyList_GetItem}{PyObject *list, Py_ssize_t index}
Return the object at position \var{pos} in the list pointed to by
- \var{p}. If \var{pos} is out of bounds, return \NULL{} and set an
- \exception{IndexError} exception.
+ \var{p}. The position must be positive, indexing from the end of the
+ list is not supported. If \var{pos} is out of bounds, return \NULL{}
+ and set an \exception{IndexError} exception.
\end{cfuncdesc}
\begin{cfuncdesc}{PyObject*}{PyList_GET_ITEM}{PyObject *list, Py_ssize_t i}