XmlNode.OwnerDocument (gb.xml)
Returns the Document object associated with this node. If it doesn't have one, this property returns 
NULL.
Unlike the W3C specification, nodes can exist without having any Document associated, because they can be simply created by using the 
NEW instruction, or by a 
XmlReader.
However, a document is automatically associated to the node, if the 
AppendChild (or siblings) method is used on it from an element that already has a Document object associated.