diff --git a/RELEASE b/RELEASE
index b2f0bca46..904b66066 100644
--- a/RELEASE
+++ b/RELEASE
@@ -1,5 +1,6 @@
                                   EYE release
 
+v10.30.4 (2024-11-19) simplify negative answer surfaces
 v10.30.3 (2024-11-13) solving issue https://github.com/eyereasoner/eye/issues/121
 v10.30.2 (2024-11-11) adjusting to https://eyereasoner.github.io/eye/#eye-color
 v10.30.1 (2024-11-08) dropping --prolog and using --n3p instead
diff --git a/VERSION b/VERSION
index f776749a0..4a8969ef5 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-10.30.3
+10.30.4
diff --git a/eye.pl b/eye.pl
index f3b5e29d3..7fc41b1e1 100644
--- a/eye.pl
+++ b/eye.pl
@@ -22,7 +22,7 @@
 :- catch(use_module(library(process)), _, true).
 :- catch(use_module(library(http/http_open)), _, true).
 
-version_info('EYE v10.30.3 (2024-11-13)').
+version_info('EYE v10.30.4 (2024-11-19)').
 
 license_info('MIT License
 
@@ -5521,7 +5521,10 @@
                 is_list(Zl),
                 is_graph(H),
                 conj_list(H, M),
-                list_to_set(M, T),
+                list_to_set(M, Ts),
+                (   T = Ts
+                ;   select(_, Ts, T)
+                ),
                 select('<http://www.w3.org/2000/10/swap/log#onNegativeSurface>'(W, O), T, N),
                 getlist(W, Wl),
                 is_list(Wl),
@@ -5581,6 +5584,26 @@
                     )
                 )), '<http://www.w3.org/2000/10/swap/log#onNegativeSurface>'(V, '<http://www.w3.org/2000/10/swap/log#onNegativeSurface>'(U, Hm)), '<>')),
 
+        % simplify negative answer surfaces
+        assertz(implies((
+                '<http://www.w3.org/2000/10/swap/log#onNegativeSurface>'(V, G),
+                getlist(V, Vl),
+                is_list(Vl),
+                is_graph(G),
+                conj_list(G, L),
+                list_to_set(L, B),
+                member('<http://www.w3.org/2000/10/swap/log#onNegativeAnswerSurface>'(_, _), B),
+                select('<http://www.w3.org/2000/10/swap/log#onNegativeSurface>'(Z, H), B, K),
+                getlist(Z, Zl),
+                is_list(Zl),
+                is_graph(H),
+                conj_list(H, M),
+                list_to_set(M, J),
+                select(_, J, T),
+                conj_list(R, T),
+                conj_list(S, ['<http://www.w3.org/2000/10/swap/log#onNegativeSurface>'(Z, R)|K])
+                ), '<http://www.w3.org/2000/10/swap/log#onNegativeSurface>'(V, S), '<>')),
+
         % resolve negative surfaces
         assertz(implies((
                 '<http://www.w3.org/2000/10/swap/log#onNegativeSurface>'(V, G),
diff --git a/eye.zip b/eye.zip
index 568c64f17..75c34a2e8 100644
Binary files a/eye.zip and b/eye.zip differ