Also a [[Reference]] can be defined on a MetaProxyProperty. If the targeted type (as set on the Reference) is a MetaProxy object the MetaProxyProperty is defined as [[ExternalPrimaryKey|External Link Property]].
If the target MetaProperty, as defined on the configuration of the MetaProxyProperty, is also a {{GUIDGuid}} property the target object of the referenced Proxy instance will be set as target value.