diff --git a/pytools/py_codegen.py b/pytools/py_codegen.py
index 25c60b48b1ba71670681d53a6bbfeee4072787aa..ed689e15ec8326c880b992af502bf592eec5b8da 100644
--- a/pytools/py_codegen.py
+++ b/pytools/py_codegen.py
@@ -23,6 +23,9 @@ THE SOFTWARE.
 """
 
 
+# loosely based on
+# http://effbot.org/zone/python-code-generator.htm
+
 class Indentation(object):
     def __init__(self, generator):
         self.generator = generator