Index: /trunk/MagicSoft/Mars/mhist/MHFalseSource.cc
===================================================================
--- /trunk/MagicSoft/Mars/mhist/MHFalseSource.cc	(revision 3577)
+++ /trunk/MagicSoft/Mars/mhist/MHFalseSource.cc	(revision 3578)
@@ -259,15 +259,19 @@
 //  ApJ 272 (1983) 317, Formula 17
 //
+//  s                    // s: number of on events
+//  b                    // b: number of off events
+//  alpha = t_on/t_off;  // t: observation time
+//
 Double_t MHFalseSource::SignificanceLiMa(Double_t s, Double_t b, Double_t alpha)
 {
-    if (s+b<=0)
+    const Double_t sum = s+b;
+
+    if (sum<=0 || alpha<=0)
         return 0;
 
-    const Double_t k = s/(s+b);
-
-    const Double_t a = s*TMath::Log(k*(alpha+1)/alpha);
-    const Double_t b = b*TMath::Log(k*(alpha+1)      );
-
-    return TMath::Sqrt((a+b)*2);
+    const Double_t l = s*TMath::Log(s/sum*(alpha+1)/alpha);
+    const Double_t m = b*TMath::Log(b/sum*(alpha+1)      );
+
+    return TMath::Sqrt((l+m)*2);
 }
 
Index: /trunk/MagicSoft/Mars/mhist/MHFalseSource.h
===================================================================
--- /trunk/MagicSoft/Mars/mhist/MHFalseSource.h	(revision 3577)
+++ /trunk/MagicSoft/Mars/mhist/MHFalseSource.h	(revision 3578)
@@ -66,4 +66,5 @@
 
     static Double_t Significance(Double_t s, Double_t b);
+    static Double_t SignificanceLiMa(Double_t s, Double_t b, Double_t alpha=1);
 
     ClassDef(MHFalseSource, 1) //3D-histogram in alpha, x and y