Attempting theming... what files do I need?

Attempting theming... what files do I need?

From looking at the source code for the demo
http://demos.jquerymobile.com/1.2.1/docs/content/content-themes.html
it looks like I need the contents of these 3:
<link rel="stylesheet"  href="../../css/themes/default/jquery.mobile-1.2.1.css" /> 
<script src="//code.jquery.com/jquery-1.7.1.min.js"></script>
<script src="../../js/jquery.mobile-1.2.1.js"></script>

However, my page is being shown minus those plus and minus signs that belong on the collapsible content. Where would these plus and minus signs be? In some other file?