Approval.

backend/hsb/basis.json

@@ -143,6 +143,9 @@
         "controlled_vocabularies": "Controlled vocabularies",
         "own_last_edits": "Own last edits",
         "contact": "Contact",
-        "uncertainty": "Uncertainty"
+        "uncertainty": "Uncertainty",
+        "certain": "Certain",
+        "uncertain": "Uncertain",
+        "unknown": "Unknown"
     }
 }