LaTeX.org

My book is structured as:
%%%%%%%%%%%%%%%%%%%%%
\include{Preamble}
\begin{document}
\frontmatter
...
\include{Preface}
\mainmatter
%%%%%%%%%%%%%%%%%%%%%
I also have:
\fancyhead[RE,LO]{\slshape \leftmark}.

On page 'vi' the upper right hand corner of the page reads "CHAPTER 0. PREFACE"

In my opinion ...

Thanks, it worked.
It should have been mention in section 3.4 of the additional features doc.

I added \enabledeprecatedfontcommands to the preamble and I get the error "Undefined Control Sequence"

I have a master lyx file with two children as a simple test situation to help my understanding of Lyx.
When I view the master as a pdf it displays OK.
I decided to add the fancy header package by doing in my master document "Document Settings->Page Layout->fancy.
In the preamble I wrote the single ...