diff --git a/32.md b/32.md
index be4e872..92497a6 100644
--- a/32.md
+++ b/32.md
@@ -151,3 +151,11 @@ A good heuristic for whether a use case fits this NIP is whether labels would ev
 For example, many events might be labeled with a particular place, topic, or pubkey, but labels
 with specific values like "John Doe" or "3.18743" are not labels, they are values, and should
 be handled in some other way.
+
+
+Appendix: Known Ontologies
+-------------------------
+
+Below is a non-exhaustive list of ontologies currently in widespread use.
+
+- (social.ontolo.categories)[https://ontolo.social/]