diff --git a/CI/CI.ml b/CI/CI.ml
index 9133690..f8f6ec4 100644
--- a/CI/CI.ml
+++ b/CI/CI.ml
@@ -410,14 +410,13 @@ let make ?(n_states=1) det_space =
 
 
 let second_order_sum { det_space ; m_H ; m_S2 ; eigensystem ; n_states }
-    list_holes  list_particles i_o1_alfa  alfa_o2_i  w_alfa =
+    list_holes  list_particles i_o1_alfa  alfa_o2_i  w_alfa  psi0 =
 
   let list_holes     = Array.of_list list_holes 
   and list_particles = Array.of_list list_particles
   in
 
   let psi0 =
-    let psi0, _ = Parallel.broadcast eigensystem in
 
     let stream = 
       Ds.determinant_stream det_space
@@ -600,7 +599,7 @@ let second_order_sum { det_space ; m_H ; m_S2 ; eigensystem ; n_states }
 let pt2_en ci =
 
   let mo_basis  = Ds.mo_basis ci.det_space in
-  let _psi0, e0 = Parallel.broadcast ci.eigensystem in
+  let psi0, e0 = Parallel.broadcast ci.eigensystem in
 
   let i_o1_alfa = h_ij mo_basis in
 
@@ -658,7 +657,7 @@ let pt2_en ci =
   in
 
   second_order_sum  ci  list_holes  list_particles
-    i_o1_alfa  i_o1_alfa  w_alfa
+    i_o1_alfa  i_o1_alfa  w_alfa  psi0
   |> List.fold_left (+.) 0.
 
 
@@ -688,8 +687,9 @@ let pt2_mp ci =
     [ MOClass.active_mos mo_class ; MOClass.virtual_mos mo_class ]
   in
 
+  let psi0, _ = Parallel.broadcast ci.eigensystem in
   second_order_sum  ci  list_holes  list_particles
-    i_o1_alfa  i_o1_alfa  w_alfa
+    i_o1_alfa  i_o1_alfa  w_alfa  psi0
   |> List.fold_left (+.) 0.
 
 
@@ -708,8 +708,9 @@ let variance ci =
     [ MOClass.active_mos mo_class ; MOClass.virtual_mos mo_class ]
   in
 
+  let psi0, _ = Parallel.broadcast ci.eigensystem in
   second_order_sum  ci  list_holes  list_particles
-    i_o1_alfa  i_o1_alfa  w_alfa
+    i_o1_alfa  i_o1_alfa  w_alfa  psi0
   |> List.fold_left (+.) 0.
 
 
diff --git a/CI/F12CI.ml b/CI/F12CI.ml
index b2240b4..e27cd82 100644
--- a/CI/F12CI.ml
+++ b/CI/F12CI.ml
@@ -47,7 +47,7 @@ let f_ij mo_basis ki kj =
   |> List.hd
 
 
-let dressing_vector ci =
+let dressing_vector ci f12_amplitudes =
 
   let mo_basis  = DeterminantSpace.mo_basis ci.CI.det_space in
 
@@ -58,28 +58,13 @@ let dressing_vector ci =
 
   let mo_class = CI.mo_class ci in
 
-  let internal_term =
-    let list_holes = List.concat
-      [ MOClass.inactive_mos mo_class ; MOClass.active_mos mo_class ]
-    and list_particles = List.concat
-      [ MOClass.active_mos mo_class ; MOClass.virtual_mos mo_class ]
-    in
-    CI.second_order_sum  ci  list_holes  list_particles
-      i_o1_alfa  alfa_o2_i  w_alfa
-    |> Vec.of_list
+  let list_holes = List.concat
+    [ MOClass.inactive_mos mo_class ; MOClass.active_mos mo_class ]
+  and list_particles = MOClass.auxiliary_mos mo_class
   in
-
-  let external_term = 
-    let list_holes = List.concat
-      [ MOClass.inactive_mos mo_class ; MOClass.active_mos mo_class ]
-    and list_particles = MOClass.auxiliary_mos mo_class
-    in
-    CI.second_order_sum  ci  list_holes  list_particles
-      i_o1_alfa  alfa_o2_i  w_alfa
-    |> Vec.of_list
-  in
-
-  Vec.sub external_term internal_term
+  CI.second_order_sum  ci  list_holes  list_particles
+      i_o1_alfa  alfa_o2_i  w_alfa  f12_amplitudes
+  |> Vec.of_list
 
 
 
diff --git a/Utils/Matrix.ml b/Utils/Matrix.ml
index 2b8b620..96c0164 100644
--- a/Utils/Matrix.ml
+++ b/Utils/Matrix.ml
@@ -576,19 +576,19 @@ let test_case () =
 
     let a = m1 and b = m2 in
     let x = ax_eq_b a b in
-    Alcotest.(check (float 1.e-10)) "dense dense 1" 0. (norm_diff (mm a x) b);
+    Alcotest.(check (float 1.e-10)) "dense  dense  1" 0. (norm_diff (mm a x) b);
 
     let a = m1 and b = m2_s in
     let x = ax_eq_b a b in
-    Alcotest.(check (float 1.e-10)) "dense dense 2" 0. (norm_diff (mm a x) b);
+    Alcotest.(check (float 1.e-10)) "dense  sparse 2" 0. (norm_diff (mm a x) b);
 
     let a = m1_s and b = m2 in
     let x = ax_eq_b a b in
-    Alcotest.(check (float 1.e-10)) "dense dense 2" 0. (norm_diff (mm a x) b);
+    Alcotest.(check (float 1.e-10)) "sparse dense  3" 0. (norm_diff (mm a x) b);
 
     let a = m1_s and b = m2_s in
     let x = ax_eq_b a b in
-    Alcotest.(check (float 1.e-10)) "dense dense 2" 0. (norm_diff (mm a x) b);
+    Alcotest.(check (float 1.e-10)) "sparse sparse 4" 0. (norm_diff (mm a x) b);
   in
 
   [