diff --git a/interp/tools.py b/interp/tools.py
index 2a9a9b4..fa91dc1 100644
--- a/interp/tools.py
+++ b/interp/tools.py
@@ -22,9 +22,13 @@ def rms(errors):
 
 def baker_exact_2D(X):
   """
-    the exact function (2D) used from baker's article (for testing)
+    the exact function (2D) used from baker's article (for testing, slightly
+    modified)
   """
   x ,y = X
+
+  # TODO: this is not baker's function!! this is:
+  #        np.power(np.sin(x*np.pi/2.0) * np.sin(y*np.pi/2.0),2)
   answer = np.power((np.sin(x * np.pi) * np.cos(y * np.pi)), 2)
   log.debug(answer)
   return answer