avoiding duplicates in XML instance

In my XML document,
I have a list of certain Elements at the global level
which need to be referenced(each multiple times) like
Pointers at various Local Scopes inside the XML
instance. How do I design an XSD to satisfy this
condition. I know you can use 'ref' inside the XSD but
that doesn't seem to serve the purpose. It will create
the Duplicate elements. 

I would like to use a sort of Pointer mechanism to
refer to these Global Elements and not duplicate the
same Element definition multiple times at various
Local scopes.   I would like some hints on how to
design such XSD.

+D

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