Annotation elaborated

Included references to EU-Spirit.

OJP_LocationSupport.xsd

@@ -184,7 +184,7 @@
 			</xs:element>
 			<xs:element name="ReferredSystemId" type="xs:normalizedString" minOccurs="0">
 				<xs:annotation>
-					<xs:documentation>If set, this topographic place resides within the given system. This system can be queried for actual locations within this topographic place. This is used in an distributed environment for a two-steps place identification.</xs:documentation>
+					<xs:documentation>Used in distributed environments (e.g. EU-Spirit). If set, this topographic place resides within the given system (in EU-Spirit "passive server"). This system can be queried for actual locations within this topographic place. This is used in an distributed environment for a two-steps place identification. In EU-Spirit the system IDs were previously called "provider code". See https://eu-spirit.eu/</xs:documentation>
 				</xs:annotation>
 			</xs:element>
 			<xs:element name="Area" minOccurs="0">