The 
                  thead element represents the collection of 
                  
                     table
                      header rows.
                  
               
The 
                  thead element represents the collection of 
                  
                     table
                      header rows.
                  
               
<table>
    <thead>
        <tr>
            <th colspan="2">Inches</th>
            <th>Lines</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <th>Length (as far as complete)</th>
            <td>17</td>
            <td>6</td>
        </tr>
    </tbody>
</table>
    This element must not contain text.
This element must contain the following children: tr
This element may contain the following children: pagebreak
http://www.daisy.org/ns/z3998/authoring/