Iterator that returns all the external reference objects of the external references object
        @rtype: L{CexternalReference}
        @return: the external reference objects

def get_external_references(self):
        """
        Iterator that returns all the external reference objects of the external references object
        @rtype: L{CexternalReference}
        @return: the external reference objects
        """
        for ext_ref_node in self.node.findall('externalRef'):
            ext_refs_obj = CexternalReference(ext_ref_node)
            for ref in ext_refs_obj:
                yield ref