remove _ from label: LaTeX rejects this due to all the magic we use to
get the _ character to format like a normal character
diff --git a/Doc/ref/ref3.tex b/Doc/ref/ref3.tex
index 50d8fa1..17da9d0 100644
--- a/Doc/ref/ref3.tex
+++ b/Doc/ref/ref3.tex
@@ -1249,7 +1249,7 @@
\end{methoddesc}
-\subsubsection{Invoking Descriptors \label{descriptor_invocation}}
+\subsubsection{Invoking Descriptors \label{descriptor-invocation}}
In general, a descriptor is an object attribute with ``binding behavior'',
one whose attribute access has been overridden by methods in the descriptor