diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/context/ContextUtilities.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/context/ContextUtilities.java
index 581a19363..b5e16816f 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/context/ContextUtilities.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/context/ContextUtilities.java
@@ -43,6 +43,8 @@ public class ContextUtilities implements ProfileKnowledgeProvider {
   private XVerExtensionManager xverManager;
   private Map<String, String> oidCache = new HashMap<>();
   private List<StructureDefinition> allStructuresList = new ArrayList<StructureDefinition>();
+  private List<String> canonicalResourceNames;
+  private List<String> concreteResourceNames;
   
   public ContextUtilities(IWorkerContext context) {
     super();
@@ -197,15 +199,19 @@ public class ContextUtilities implements ProfileKnowledgeProvider {
    * @return a list of the resource names that are canonical resources defined for this version
    */
   public List<String> getCanonicalResourceNames() {
-    List<String> names = new ArrayList<>();
-    for (StructureDefinition sd : allStructures()) {
-      if (sd.getKind() == StructureDefinitionKind.RESOURCE && !sd.getAbstract() && hasUrlProperty(sd)) {
-        names.add(sd.getType());
+    if (canonicalResourceNames == null) {
+      canonicalResourceNames =  new ArrayList<>();
+      Set<String> names = new HashSet<>();
+      for (StructureDefinition sd : allStructures()) {
+        if (sd.getKind() == StructureDefinitionKind.RESOURCE && !sd.getAbstract() && hasUrlProperty(sd)) {
+          names.add(sd.getType());
+        }
       }
+      canonicalResourceNames.addAll(Utilities.sorted(names));
     }
-    return names;
+    return canonicalResourceNames;
   }
-    
+
   /**
    * @return a list of all structure definitions, with snapshots generated (if possible)
    */
@@ -370,5 +376,19 @@ public class ContextUtilities implements ProfileKnowledgeProvider {
     return null;
   }
 
+  public List<String>  getConcreteResources() {
+    if (concreteResourceNames == null) {
+      concreteResourceNames =  new ArrayList<>();
+      Set<String> names = new HashSet<>();
+      for (StructureDefinition sd : allStructures()) {
+        if (sd.getKind() == StructureDefinitionKind.RESOURCE && !sd.getAbstract()) {
+          names.add(sd.getType());
+        }
+      }
+      concreteResourceNames.addAll(Utilities.sorted(names));
+    }
+    return concreteResourceNames;
+  }
+
 }
 
diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/renderers/ResourceRenderer.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/renderers/ResourceRenderer.java
index c9d57ba5d..e848bcff6 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/renderers/ResourceRenderer.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/renderers/ResourceRenderer.java
@@ -223,12 +223,15 @@ public abstract class ResourceRenderer extends DataRenderer {
       tr = resolveReference(rw, r.getReference());
 
       if (!r.getReference().startsWith("#")) {
-        if (tr != null && tr.getReference() != null)
+        if (tr != null && tr.getReference() != null) {
           c = x.ah(tr.getReference());
-        else
+        } else if (r.getReference().contains("?")) {
+          x.tx("Conditional Reference: ");
+          c = x.code("");
+        } else {
           c = x.ah(r.getReference());
+        }
       } else {
-        
         c = x.ah(r.getReference());
       }
     } else {
diff --git a/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/xhtml/XhtmlFluent.java b/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/xhtml/XhtmlFluent.java
index 93f1158d0..75a9b456f 100644
--- a/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/xhtml/XhtmlFluent.java
+++ b/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/xhtml/XhtmlFluent.java
@@ -150,7 +150,9 @@ public abstract class XhtmlFluent {
 
 
   public XhtmlNode code(String text) {
-    return addTag("code").tx(text);
+    XhtmlNode code = addTag("code");
+    code.tx(text);
+    return code;
   }
 
   public XhtmlNode code() {