In a beamer presentation using:

\documentclass[dvipsnames,pdflatex,beamer,compress]{beamer}
%\usepackage{SweaveSlides}
\usepackage{mdwlist}
\usepackage[comma]{natbib}
.....

\mode<beamer>{%
   \usetheme{Copenhagen}
....
}

\begin{frame}
   \frametitle{Outline}
   \tableofcontents[hideallsubsections]
\end{frame}
....


I include citations in slides and finish with

\begin{frame}[allowframebreaks]
\frametitle{References}
{\small
\bibliography{graphics,Rpackages}
}
\end{frame}

References does not appear in the Outline, but it does appear in the top 
line showing the Section abbreviations.  How can I suppress References 
there?

-Michael