diff --git a/grammars/isodoc.rnc b/grammars/isodoc.rnc
index 26d0ad7..aeb4420 100644
--- a/grammars/isodoc.rnc
+++ b/grammars/isodoc.rnc
@@ -162,7 +162,7 @@ sourcecode =
     attribute lang { text }?,
     BlockAttributes,
     attribute linenums { xsd:boolean }?,
-    tname?, ( text | callout )+, annotation*, note*
+    tname?, ( text | callout | xref | eref )+, annotation*, note*
   }
 
 formula =
diff --git a/grammars/isodoc.rng b/grammars/isodoc.rng
index 2b1d1ee..ea74ded 100644
--- a/grammars/isodoc.rng
+++ b/grammars/isodoc.rng
@@ -484,6 +484,8 @@
           <choice>
             <text/>
             <ref name="callout"/>
+            <ref name="xref"/>
+            <ref name="eref"/>
           </choice>
         </oneOrMore>
         <zeroOrMore>
diff --git a/grammars/relaton-models b/grammars/relaton-models
index d7115ee..64718de 160000
--- a/grammars/relaton-models
+++ b/grammars/relaton-models
@@ -1 +1 @@
-Subproject commit d7115ee43416a2d3bd0b050cda687504282f247e
+Subproject commit 64718de5b6858cbd07f617dd7365bb972d84c453