Hi Martin.
1. Compare xml is not correct method in my case. Many nodes can has same xml - think about XHTML document. I need a method for refs compare.
2.

VFP "add" property previousSibling to VFP object e1
...
e0N has not property previousSibling

It is not so. e1 and e0N is refs to XMLDOM objects and have readonly prop previousSibling.