Add a note about yield requiring a __future__ directive.
diff --git a/Doc/ref/ref6.tex b/Doc/ref/ref6.tex
index 1f1486b..3089b1a 100644
--- a/Doc/ref/ref6.tex
+++ b/Doc/ref/ref6.tex
@@ -482,6 +482,16 @@
resumed, hence no guarantee that the \keyword{finally} block will ever
get executed.
+\note{In Python 2.2, the \keyword{yield} statement is only allowed
+when the \code{generators} feature has been enabled. It will always
+be enabled in Python 2.3. This \code{__future__} import statment can
+be used to enable the feature:}
+
+\begin{verbatim}
+from __future__ import generators
+\end{verbatim}
+
+
\begin{seealso}
\seepep{0255}{Simple Generators}
{The proposal for adding generators and the \keyword{yield}