How to parse xml referencing another xml's relative path in element, using xmltextreader in c#?

Question

I have a xml as following,

 <FixedPage Width="816" Height="1056" 
 xmlns="http://schemas.microsoft.com/xps/2005/06" xml:lang="und">
    <!-- Microsoft XPS Document Converter (MXDC) Generated! Version: 
 0.3.15063.138 -->
    <FixedPage.Resources>
        <ResourceDictionary Source="/Resources/_D1.dict" />
    </FixedPage.Resources>'
 ...
 ...
 ...
 </FixedPage>

The Source '/Resources/_D1.dict' is another xml. How do I include this xml to parse using xmltextreader?