Update control.rng

Made `<reference>` mandatory and not repeatable within `<source>` according to #107
SAA-SDT · Nov 5, 2020 · 8fdd087 · 8fdd087
1 parent 9b7fa69
commit 8fdd087
Showing 1 changed file with 1 addition and 3 deletions.
diff --git a/source/modules/control.rng b/source/modules/control.rng
@@ -212,9 +212,7 @@
             <ref name="attribute-group.global-plus-lang-and-script.optional"/>
             <ref name="attribute-group.links.optional"/>
             <ref name="attribute.lastDateTimeVerified.optional"/>
-            <optional>
-                <ref name="element.reference"/>    
-            </optional>
+            <ref name="element.reference"/>
             <zeroOrMore>
                 <element name="citedRange">
                     <ref name="attribute-group.global.optional"/>