private XmlNamespaceManager GetNamespaceManager()
{
_ns = new XmlNamespaceManager(new NameTable());
_ns.AddNamespace("dc", "http://purl.org/dc/elements/1.1/");
_ns.AddNamespace("opf", "http://www.idpf.org/2007/opf");
_ns.AddNamespace("epub", "http://www.idpf.org/2007/ops");
_ns.AddNamespace("xhtml", "http://www.w3.org/1999/xhtml");
_ns.AddNamespace("smil", "http://www.w3.org/ns/SMIL");
return _ns;
}