Document structure

The |book| document class introduces new commands to indicate document structure.
\begin{decl}
\vert\frontmatter\vert \\ Vert\mainmatter\vert \\ Vert\backmatter\vert
\end{decl}
These commands indicate the beginning of the front matter (title page, table of contents and prefaces), main matter (main text) and back matter (bibliography, indexes and colophon).