diff --git a/python/dune/perftool/ufl/transformations/argument_elimination.py b/python/dune/perftool/ufl/transformations/argument_elimination.py
index 70cc660c692cb6508f4343d9a62786e08407f47d..4bb6c80e693a8f757d8ed3939baee52cef30c634 100644
--- a/python/dune/perftool/ufl/transformations/argument_elimination.py
+++ b/python/dune/perftool/ufl/transformations/argument_elimination.py
@@ -1,9 +1,22 @@
+"""
+Define an UFL MultiFunction that removes the modified arguments from
+a given UFL expression(, which represents one accumumlation term).
+
+Examples:
+e1=e2*v => (e2, (v, ))
+e1=e2*v*w => (e2, (v, w))
+
+Note that in PDELab, only test functions are arguments!
+Trial functions are coefficients instead.
+"""
 from __future__ import absolute_import
 from ufl.algorithms import MultiFunction
 
 
 class EliminateArguments(MultiFunction):
-    """ Application scope: Take a valid accumulation term and remove the modified argument from it! """
+    """ This MultiFunction processes the expression bottom up and replaces
+    all modified argument by None and eliminates all None-Terms afterwards.
+    """
     call = MultiFunction.__call__
 
     def __call__(self, o):
diff --git a/python/dune/perftool/ufl/transformations/extract_accumulation_terms.py b/python/dune/perftool/ufl/transformations/extract_accumulation_terms.py
index c869f2e64ee86e9ec16276c652fd79223f9497cb..7f64f65b4e241c3bd2f85f25b558a522bc22e0b2 100644
--- a/python/dune/perftool/ufl/transformations/extract_accumulation_terms.py
+++ b/python/dune/perftool/ufl/transformations/extract_accumulation_terms.py
@@ -1,3 +1,8 @@
+"""
+This module defines an UFL transformation, that takes a UFL expression
+and transforms it into a sum of terms that all contain the correct number
+of test function terms (which is equal to the form rank).
+"""
 from __future__ import absolute_import
 from ufl.algorithms import MultiFunction