diff --git a/lib/resource-1.0/TODO b/lib/resource-1.0/TODO
index 63b89aa1b..a43e0815a 100644
--- a/lib/resource-1.0/TODO
+++ b/lib/resource-1.0/TODO
@@ -36,5 +36,6 @@ API: multimodal/: dialogue-specific lexicon
 
 API: swadesh/: build a swadesh-related API and migrate lexica
 
+API: mathematical/: symbolic formulas as Cl