Index: trunk/MagicSoft/TDAS-Extractor/Criteria.tex
===================================================================
--- trunk/MagicSoft/TDAS-Extractor/Criteria.tex	(revision 6578)
+++ trunk/MagicSoft/TDAS-Extractor/Criteria.tex	(revision 6579)
@@ -10,9 +10,12 @@
 Those considered as signal are further used to compute the image parameters while the background ones are simply rejected. The calculation 
 of the second moments of the image ``ellipse'' usually fails when applied to un-cleaned images, therefore the decision is yes or 
-no\footnote{This restriction is not necessary any more in all advanced analyses using likelihood fits to the images or fourier transforms}. 
+no\footnote{This restriction is not necessary any more in all advanced analyses using likelihood fits to the images or fourier transforms. Thereby any bias of the reconstructed signal leads to potentially wrong results.}. 
 Moreover,
 already low contributions of mis-estimated background can degrade the resolution of the image parameters considerably. If one wants to 
 lower the threshold for signal recognition, it is therefore mandatory to increase the efficiency with which the background is recognized as 
 such. If the background resolution is bad, the signal threshold goes up and vice versa.
+
+Also an accurate determination of the signal arrival time may help to distinguish between signal and background. The signal arrival times vary smoothly from pixel to pixel while the background noise is randomly distributed in time.
+
 \par
 One cuts on the probability that the reconstructed charge is due to background. This yields a lower reconstructed signal limit for an event