[texhax] Adding separators and fixed text to the TOC

[Luca Turchetti]

I would like to add an heading to separate the appendices from the
chapters in the TOC, i.e.

1 Chapter one title                                                 1
    1.1 Section title ..............................................2
    1.2 Section title ..............................................4

APPENDIX

A Appendix A title                                                 40
    A.1 Title .....................................................41

I'm trying to use the \addtocontents command just before \appendix, i.e.
(I'm not still sure about the style I want "APPENDIX" to be typeset)

\addtocontents{toc}{{\protect\Large\bfseries APPENDIX} \hrule}

This works, but

\addtocontents{toc}{{\protect\Large\bfseries APPENDIX}}

doesn't. Similarly, I'm not free to use many other ordinary LaTeX
typesetting commands. I think I have to better understand the protection
of the commands passed as arguments of \addtocontents.

Where could I find a detailed documentation of this use of
\addtocontents? Is there another way of doing such a thing?

Thank you
Luca Turchetti