diff --git a/as_covers/as_cover_class.sage b/as_covers/as_cover_class.sage
index 0659b29..8117715 100644
--- a/as_covers/as_cover_class.sage
+++ b/as_covers/as_cover_class.sage
@@ -314,8 +314,9 @@ class as_cover:
         g = self.genus()
         return g - self.cartier_matrix().rank()
 
-    def cohomology_of_structure_sheaf_basis(self, threshold = 8):
-        holo_diffs = self.holomorphic_differentials_basis(threshold = threshold)
+    def cohomology_of_structure_sheaf_basis(self, holo_basis = 0, threshold = 8):
+        if holo_basis == 0:
+            holo_basis = self.holomorphic_differentials_basis(threshold = threshold)
         from itertools import product
         x_series = self.x_series
         y_series = self.y_series
@@ -341,7 +342,7 @@ class as_cover:
             for j in range(0, m):
                 for k in product(*pr):
                     f = as_function(self, prod(z[i1]^(k[i1]) for i1 in range(n))/x^i*y^j)
-                    f_products = [omega.serre_duality_pairing(f) for omega in holo_diffs]
+                    f_products = [omega.serre_duality_pairing(f) for omega in holo_basis]
                     if vector(f_products) not in S:
                         S = S+V.subspace([V(f_products)])
                         result_fcts += [f]
@@ -384,11 +385,15 @@ class as_cover:
                     return a*omega + fct.diffn()
         raise ValueError("Unknown.")
 
-    def de_rham_basis(self, threshold = 30):
+    def de_rham_basis(self, holo_basis = 0, cohomology_basis = 0, threshold = 30):
+        if holo_basis == 0:
+            holo_basis = self.holomorphic_differentials_basis(threshold = threshold)
+        if cohomology_basis == 0:
+            cohomology_basis = self.cohomology_of_structure_sheaf_basis(holo_basis = holo_basis, threshold = threshold)
         result = []
-        for omega in self.holomorphic_differentials_basis(threshold = threshold):
+        for omega in holo_basis:
             result += [as_cech(self, omega, as_function(self, 0))]
-        for f in self.cohomology_of_structure_sheaf_basis(threshold = threshold):
+        for f in cohomology_basis:
             omega = self.lift_to_de_rham(f, threshold = threshold)
             result += [as_cech(self, omega, f)]
         return result
diff --git a/as_covers/group_action_matrices.sage b/as_covers/group_action_matrices.sage
index 7fb6528..3aad125 100644
--- a/as_covers/group_action_matrices.sage
+++ b/as_covers/group_action_matrices.sage
@@ -27,7 +27,10 @@ def group_action_matrices_dR(AS, threshold=8):
         ei = n*[0]
         ei[i] = 1
         generators += [ei]
-    basis = [AS.holomorphic_differentials_basis(threshold = threshold), AS.cohomology_of_structure_sheaf_basis(threshold = threshold), AS.de_rham_basis(threshold=threshold)]
+    holo_basis = AS.holomorphic_differentials_basis(threshold = threshold)
+    str_basis = AS.cohomology_of_structure_sheaf_basis(holo_basis = holo_basis, threshold = threshold)
+    dr_basis = AS.de_rham_basis(holo_basis = holo_basis, cohomology_basis = str_basis, threshold=threshold)
+    basis = [holo_basis, str_basis, dr_basis]
     return group_action_matrices(basis[2], generators, basis = basis)
     
 def group_action_matrices_old(C_AS):