XML : Who to read XML file of below content into Xdocument

How can I read below content from a XML file into XDocument. How ever the resulting XDocument should not contain " <!DOCTYPE math:math PUBLIC "-//OpenOffice.org//DTD Modified W3C MathML 1.01//EN" "math.dtd">"

  <?xml version="1.0" encoding="UTF-8"?>      <!DOCTYPE math:math PUBLIC "-//OpenOffice.org//DTD Modified W3C MathML 1.01//EN" "math.dtd">      <math:math xmlns:math="http://www.w3.org/1998/Math/MathML">          <math:semantics>              <math:msup>                  <math:mrow>                      <math:mo math:stretchy="false">(</math:mo>                      <math:mrow>                          <math:mi>a</math:mi>                          <math:mo math:stretchy="false">+</math:mo>                          <math:mi>b</math:mi>                      </math:mrow>                      <math:mo math:stretchy="false">)</math:mo>                  </math:mrow>                  <math:mn>2</math:mn>              </math:msup>              <math:annotation math:encoding="StarMath 5.0">(a+b)^2</math:annotation>          </math:semantics>      </math:math>