Using vsoWebControl.findRelation with vCloud objects

I'm consuming the Orchestrator Web Service from an C#.NET application.

I have problems listing vDCs into an Organization.

I can found an Organization object with this lines:

VSOWebControlClient webcontrol = new VSOWebControlClient();

QueryResult q1 = webcontrol.find("vCloud:Organization", orgName, user, pass);

But the following line always returns -1:

webcontrol.hasChildrenInRelation("vCloud:Organization", dunesUri, RELATION, user, pass);

The vcenter-orchestrator-51-develop-web-services-guide.pdf only mention the vCenter Server Relation Types. I've tried with every one of this with no result.

Can you help me with this? Do you know the vCloud Server Relation Types?

Thanks a lot.

Damián