PG hit a markup issue: the 1609 Sonnet document has two distinct works in it, and the second of them has as elaborate a title page as the first, occurring in the middle of the document. However, the <titlePage> tag only seems to be able to appear in a <front> tag, which cannot appear after a <body>. I think the obvious solution is shown here, and looks like this:
<text>
<front/>
<group>
<text>
<front/>
<body/>
<back/>
</text>
<text/>
</group>
</text>
The frontispiece/title page material that applies to the whole document comes first, in the root text, and then the two component documents are enclosed in a <group> tag, each being a full <text> element.
