			href="epub-spec.html#dfn-xhtml-content-document">XHTML Content Documents</a>, <a
								href="epub-spec.html#dfn-svg-content-document">SVG Content Documents</a>, CSS Style
							Sheets and <a href="epub-spec.html#dfn-media-overlay-document">Media Overlay
							Documents</a>).</td>
					</tr>
					<tr>
						<th>Cardinality:</th>
						<td>
							<code>Zero or more</code>
						</td>
					</tr>
					<tr>
						<th>Usage:</th>
						<td>MUST be set if and only if the criterion specified in the descript