<chapt> tag, followed by the
chapter's title. The title may contain marked-up inline text, but no
cross-references (see Marked-up inline text and character style markup, chapter 4).
The body of the chapter is zero or more paragraphs, the first of which
must be indicated by a <p> tag to distinguish it from the
title, and then zero or more sections.
A section starts with <sect>, and has a similar structure:
title, optionally some paragraphs, and then optionally some
subsections.
Subsections are <sect1>; there are also smaller divisions
<sect2>, <sect3> and <sect4>.
Paragraphs are introduced by <p>. Sometimes the start of
paragraph tag can be omitted, but it is mandatory after
<chapt>, <sect> and so forth. It is never
necessary to mark the end of a paragraph with </p>.
Paragraphs can contain marked up inline text (see Marked-up inline text and character style markup, chapter 4) and also lists and examples (Lists and examples , chapter 5).