diff --git a/concordia/t/test_tm_matches.cpp b/concordia/t/test_tm_matches.cpp
index 5cc3108..484bfcc 100644
--- a/concordia/t/test_tm_matches.cpp
+++ b/concordia/t/test_tm_matches.cpp
@@ -17,4 +17,32 @@ BOOST_AUTO_TEST_CASE( TmMatchesSimpleScore1 )
     BOOST_CHECK_EQUAL(tmMatches.getScore(),0.35);
 }
 
+BOOST_AUTO_TEST_CASE( TmMatchesLogarithmicScore1 )
+{
+    TmMatches tmMatches(0,10,10);
+    tmMatches.calculateScore();
+    
+    BOOST_CHECK_EQUAL(tmMatches.getScore(),0.0);
+}
+
+BOOST_AUTO_TEST_CASE( TmMatchesLogarithmicScore2 )
+{
+    TmMatches tmMatches(0,10,10);
+    tmMatches.addPatternInterval(0,10);
+    tmMatches.addExampleInterval(0,10);
+    tmMatches.calculateScore();
+    
+    BOOST_CHECK_EQUAL(tmMatches.getScore(),1.0);
+}
+
+BOOST_AUTO_TEST_CASE( TmMatchesLogarithmicScore3 )
+{
+    TmMatches tmMatches(0,10,10);
+    tmMatches.addPatternInterval(2,5);
+    tmMatches.addExampleInterval(1,5);
+    tmMatches.calculateScore();
+    
+    BOOST_CHECK_CLOSE(tmMatches.getScore(),0.2482, 0.1);
+}
+
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/concordia/tm_matches.cpp b/concordia/tm_matches.cpp
index 4b7c8ca..178221f 100644
--- a/concordia/tm_matches.cpp
+++ b/concordia/tm_matches.cpp
@@ -1,6 +1,6 @@
 #include "concordia/tm_matches.hpp"
 #include <boost/foreach.hpp>
-
+#include <math.h>
 
 TmMatches::TmMatches(const SUFFIX_MARKER_TYPE exampleId,
                        const unsigned char exampleSize,
@@ -14,20 +14,13 @@ TmMatches::~TmMatches() {
 }
 
 void TmMatches::calculateScore() {
-    /* TODO logarithmic function
-	unsigned char exampleMatchedLength = 0;
-	BOOST_FOREACH(Interval & interval, _exampleMatchedRegions) {
-		exampleMatchedLength += interval.getLength();
-	}
 
-	unsigned char patternMatchedLength = 0;
-	BOOST_FOREACH(Interval & interval, _patternMatchedRegions) {
-		patternMatchedLength += interval.getLength();
-	}
-
-	_score = (double) (exampleMatchedLength + patternMatchedLength)
-			/ (double) (_exampleSize + _patternSize);
-    */
+    double exampleOverlay = _getLogarithmicOverlay(_exampleMatchedRegions,
+                                                   _exampleSize, 1.0);
+                                                   
+    double patternOverlay = _getLogarithmicOverlay(_patternMatchedRegions,
+                                                   _patternSize, 2.0);
+	_score = (exampleOverlay + patternOverlay) / 2.0;
 }
 
 void TmMatches::calculateSimpleScore() {
@@ -72,3 +65,17 @@ bool TmMatches::_alreadyIntersects(
 	return false;
 }
 
+double TmMatches::_getLogarithmicOverlay(boost::ptr_vector<Interval> intervalList,
+                             unsigned char sentenceSize,
+                             double k) {
+    double overlayScore = 0;
+	BOOST_FOREACH(Interval & interval, intervalList) {
+        double intervalOverlay = (double) interval.getLength() / (double) sentenceSize;
+        double significanceFactor = pow(log(interval.getLength()+1) / log(sentenceSize+1), 1/k);
+        
+        overlayScore += intervalOverlay * significanceFactor;
+	}
+    return overlayScore;                            
+}
+
+
diff --git a/concordia/tm_matches.hpp b/concordia/tm_matches.hpp
index fee8f6f..12748fb 100644
--- a/concordia/tm_matches.hpp
+++ b/concordia/tm_matches.hpp
@@ -44,6 +44,10 @@ private:
     bool _alreadyIntersects(boost::ptr_vector<Interval> intervalList,
                            int start, int end);
     
+    double _getLogarithmicOverlay(boost::ptr_vector<Interval> intervalList,
+                                 unsigned char sentenceSize,
+                                 double k);
+    
 	SUFFIX_MARKER_TYPE _exampleId;
 
 	boost::ptr_vector<Interval> _exampleMatchedRegions;