diff --git a/docs/source/conf.py b/docs/source/conf.py
index 8a0977c2..01d80fd6 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -94,7 +94,8 @@
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
 
-mathjax_config = {                  
+mathjax_path = 'https://cdn.jsdelivr.net/npm/mathjax@2/MathJax.js?config=TeX-AMS-MML_HTMLorMML'
+mathjax3_config = {
     "TeX": {         
         #"packages": {'[+]': ['bm']},
         "Macros": {
diff --git a/e2cnn/group/groups/cyclicgroup.py b/e2cnn/group/groups/cyclicgroup.py
index 0e5c2665..abcaa142 100644
--- a/e2cnn/group/groups/cyclicgroup.py
+++ b/e2cnn/group/groups/cyclicgroup.py
@@ -149,8 +149,8 @@ def subgroup(self, id: int) -> Tuple[Group, Callable, Callable]:
             # take the elements of the group generated by "r^ratio"
             sg = CyclicGroup(order)
     
-            parent_mapping = lambda e, ratio=ratio: e * ratio
-            child_mapping = lambda e, ratio=ratio: None if e % ratio != 0 else int(e // ratio)
+            parent_mapping = ParentMapping(ratio=ratio)
+            child_mapping = ChildMapping(ratio=ratio)
             
             self._subgroups[id] = sg, parent_mapping, child_mapping
     
@@ -260,17 +260,14 @@ def irrep(self, k: int) -> IrreducibleRepresentation:
             if k == 0:
                 # Trivial representation
             
-                irrep = lambda element, identity=np.eye(1): identity
-                character = lambda e: 1
+                irrep = get_trivial_representation
                 supported_nonlinearities = ['pointwise', 'gate', 'norm', 'gated', 'concatenated']
                 self.irreps[name] = IrreducibleRepresentation(self, name, irrep, 1, 1,
                                                               supported_nonlinearities=supported_nonlinearities,
-                                                              # character=character,
-                                                              # trivial=True,
                                                               frequency=k)
             elif n % 2 == 0 and k == int(n/2):
                 # 1 dimensional Irreducible representation (only for even order groups)
-                irrep = lambda element, k=k, base_angle=base_angle: np.array([[np.cos(k * element * base_angle)]])
+                irrep = OneDimRepresentation(k, base_angle)
                 supported_nonlinearities = ['norm', 'gated', 'concatenated']
                 self.irreps[name] = IrreducibleRepresentation(self, name, irrep, 1, 1,
                                                               supported_nonlinearities=supported_nonlinearities,
@@ -279,7 +276,7 @@ def irrep(self, k: int) -> IrreducibleRepresentation:
                 # 2 dimensional Irreducible Representations
                 
                 # build the rotation matrix with rotation frequency 'frequency'
-                irrep = lambda element, k=k, base_angle=base_angle: utils.psi(element * base_angle, k=k)
+                irrep = TwoDimRepresentation(k, base_angle)
             
                 supported_nonlinearities = ['norm', 'gated']
                 self.irreps[name] = IrreducibleRepresentation(self, name, irrep, 2, 2,
@@ -295,3 +292,54 @@ def _generator(N: int) -> 'CyclicGroup':
         
         return _cached_group_instances[N]
 
+           # parent_mapping = lambda e, ratio=ratio: e * ratio
+           # child_mapping = lambda e, ratio=ratio: None if e % ratio != 0 else int(e // ratio)
+    
+class ParentMapping:
+
+    def __init__(self, ratio):
+        self.ratio = ratio
+
+    def __call__(self, e, ratio=None):
+        ratio = ratio if bool(ratio) else self.ratio
+        return e * ratio
+
+
+class ChildMapping:
+
+    def __init__(self, ratio):
+        self.ratio = ratio
+
+    def __call__(self, e, ratio=None):
+        ratio = ratio if bool(ratio) else self.ratio
+        return None if e % ratio != 0 else int(e // ratio)
+
+
+
+def get_trivial_representation(element, identity=np.eye(1)):
+    return identity
+
+
+class OneDimRepresentation:
+
+    def __init__(self, k, base_angle):
+        self.k = k
+        self.base_angle = base_angle
+
+    def __call__(self, element, k=None, base_angle=None):
+        k = k if bool(k) else self.k
+        base_angle = base_angle if bool(base_angle) else self.base_angle
+
+        return np.array([[np.cos(k * element * base_angle)]])
+
+
+class TwoDimRepresentation:
+
+    def __init__(self, k, base_angle):
+        self.k = k
+        self.base_angle = base_angle
+
+    def __call__(self, element, k=None, base_angle=None):
+        k = k if bool(k) else self.k
+        base_angle = base_angle if bool(base_angle) else self.base_angle
+        return utils.psi(element * base_angle, k=k)
\ No newline at end of file
diff --git a/e2cnn/group/representation.py b/e2cnn/group/representation.py
index 1647f252..60fb51b7 100644
--- a/e2cnn/group/representation.py
+++ b/e2cnn/group/representation.py
@@ -737,14 +737,6 @@ def build_regular_representation(group: e2cnn.group.Group) -> Tuple[List[e2cnn.g
     change_of_basis_inv = change_of_basis.T
     
     return irreps, change_of_basis, change_of_basis_inv
-    
-    # return Representation(group,
-    #                       "regular",
-    #                       [r.name for r in irreps],
-    #                       change_of_basis,
-    #                       ['pointwise', 'norm', 'gated', 'concatenated'],
-    #                       representation=representation,
-    #                       change_of_basis_inv=change_of_basis_inv)
 
 
 def build_quotient_representation(group: e2cnn.group.Group,
@@ -1048,10 +1040,36 @@ def direct_sum_factory(irreps: List[e2cnn.group.IrreducibleRepresentation],
     
     unique_irreps = list({irr.name: irr for irr in irreps}.items())
     irreps_names = [irr.name for irr in irreps]
-    
-    def direct_sum(element,
-                   irreps_names=irreps_names, change_of_basis=change_of_basis,
-                   change_of_basis_inv=change_of_basis_inv, unique_irreps=unique_irreps):
+
+    return DirectSum(
+        irreps_names=irreps_names,
+        change_of_basis=change_of_basis,
+        change_of_basis_inv=change_of_basis_inv,
+        unique_irreps=unique_irreps
+    )
+
+
+class DirectSum:
+
+    def __init__(self, irreps_names, change_of_basis, change_of_basis_inv, unique_irreps):
+        self.irreps_names = irreps_names
+        self.change_of_basis = change_of_basis
+        self.change_of_basis_inv = change_of_basis_inv
+        self.unique_irreps = unique_irreps
+
+    def __call__(
+        self, 
+        element,
+        irreps_names=None, 
+        change_of_basis=None,
+        change_of_basis_inv=None, 
+        unique_irreps=None
+    ):
+        irreps_names = irreps_names if bool(irreps_names) else self.irreps_names
+        change_of_basis = change_of_basis if bool(change_of_basis) else self.change_of_basis
+        change_of_basis_inv = change_of_basis_inv if bool(change_of_basis_inv) else self.change_of_basis_inv
+        unique_irreps = unique_irreps if bool(unique_irreps) else self.unique_irreps
+
         reprs = {}
         for n, irr in unique_irreps:
             reprs[n] = irr(element)
@@ -1064,8 +1082,6 @@ def direct_sum(element,
         P = sparse.block_diag(blocks, format='csc')
         
         return change_of_basis @ P @ change_of_basis_inv
-    
-    return direct_sum
 
 
 def null(A: Union[np.matrix, sparse.linalg.LinearOperator],
diff --git a/e2cnn/gspaces/r2/general_r2.py b/e2cnn/gspaces/r2/general_r2.py
index b0f6f8a0..d83a55c2 100644
--- a/e2cnn/gspaces/r2/general_r2.py
+++ b/e2cnn/gspaces/r2/general_r2.py
@@ -34,7 +34,7 @@ def __init__(self, fibergroup: Group, name: str):
         # Store the computed intertwiners between irreps
         # - key = (filter size, sigma, rings)
         # - value = dictionary mapping (input_irrep, output_irrep) pairs to the corresponding basis
-        self._irreps_intertwiners_basis_memory = defaultdict(lambda: dict())
+        self._irreps_intertwiners_basis_memory = defaultdict(dict)
 
         # Store the computed intertwiners between general representations
         # - key = (filter size, sigma, rings)
diff --git a/e2cnn/kernels/basis.py b/e2cnn/kernels/basis.py
index 50c5e8a1..edd6cbc9 100644
--- a/e2cnn/kernels/basis.py
+++ b/e2cnn/kernels/basis.py
@@ -124,7 +124,7 @@ def sample_masked(self, points: np.ndarray, mask: np.ndarray, out: np.ndarray =
         """
         
         assert mask.shape == (self.dim, )
-        assert mask.dtype == np.bool
+        assert mask.dtype == bool
 
         basis = self.sample(points)
         
diff --git a/e2cnn/nn/modules/r2upsampling.py b/e2cnn/nn/modules/r2upsampling.py
index 369c95e2..7d827543 100644
--- a/e2cnn/nn/modules/r2upsampling.py
+++ b/e2cnn/nn/modules/r2upsampling.py
@@ -35,7 +35,7 @@ def __init__(self,
         However, ``"nearest"`` is not equivariant; using this method may result in broken equivariance.
         For this reason, we suggest to use ``"bilinear"`` (default value).
 
-        ..warning ::
+        .. warning ::
             The module supports a ``size`` parameter as an alternative to ``scale_factor``.
             However, the use of ``scale_factor`` should be *preferred*, since it guarantees both axes are scaled
             uniformly, which preserves rotation equivariance.