diff --git a/sage/period_computation.sage b/sage/period_computation.sage
index e3d0017..9d8b457 100644
--- a/sage/period_computation.sage
+++ b/sage/period_computation.sage
@@ -1,9 +1,11 @@
-import logger
+import logging
 from sage.all import sage_eval, PolynomialRing, QQ
 
 class PFOperator:
     """
     A class representing a Picard-Fuchs operator in a single variable z.
+    Independent of the given order, the variables are assumed to be left of
+    the derivatives.
     """
     def _operator_from_string(self, operator_string):
         z_names = ['z%d' % i for i in range(self.no_variables)]
@@ -21,5 +23,6 @@ class PFOperator:
     def __init__(self, operator_string, no_variables=1):
         self.no_variables = no_variables
         self.operator = self._operator_from_string(operator_string)
+        logging.debug("Initialized PFOperator: %s", self.operator)
     
     
\ No newline at end of file