How to use the method libxml++ to write a file in c ++ xml

[stepner03]

I'm using libxml++ library in C++, and I have to write an xml file in which there is an inclusion of another xml file:

1 <? Xml version = "1.0"?>
2 <! DOCTYPE EXAMPLE [
3 <! ENTITY xml "exampl2.xml">
4]>
5 <example>
6 &xml;
7 </ example>

I saw the classes Document, Element, ..... but I have not found any method to use to write code in my xml file line 6, while for lines 2-3-4, I used these methods:

Document* Doc;

Doc.set_internal_subset ("EXAMPLE","","");
Doc.set_entity_declaration ("xml",XML_EXTERNAL_GENERAL_PARSED_ENTITY,"","example2.xml","");

Thanks.