Add sources to project

I create project in Eclipse, for that i use this tutorial - http://goo.gl/7bY3H
The project has started properly on the device. Next, I needed parse the xml file, for this I used tinyXml - http://goo.gl/UCbGf
I put the source in a folder Classes/tinyXml/
then in HelloWorldScene.cpp I added #include “tinyXml/tinyxml.h” and this lines:
TiXmlDocument* doc = new TiXmlDocument (“demo.xml”);
doc->LoadFile ();
But I get the errors:
“undefined reference to `TiXmlDocument::TiXmlDocument(char const**)’”
“undefined reference to `TiXmlDocument::LoadFile(TiXmlEncoding)’”
**Solved*: I add in Android.mk this line:
…/…/Classes/tinyXml/tinyxml.cpp …/…/Classes/tinyXml/tinyxmlparser.cpp …/…/Classes/tinyXml/tinyxmlerror.cpp …/…/Classes/tinyXml/tinystr.cpp