diff --git a/docs/source/metric.rst b/docs/source/metric.rst
index cce98d9..aeff236 100644
--- a/docs/source/metric.rst
+++ b/docs/source/metric.rst
@@ -4,6 +4,7 @@
 
 To obtain simulation results, you would need to connect to one or more `trace sources <doxygen/group___trace_source_list.html>`_ provided by ndnSIM classes.
 
+.. _trace classes:
 
 Tracer classes
 --------------
@@ -20,12 +21,19 @@
 
     .. code-block:: c++
 
+        // necessary includes
+	#include <ns3/ndnSIM/utils/tracers/ndn-l3-aggregate-tracer.h>
+
+	...        
+
         // the following should be put just before calling Simulator::Run in the scenario
 
-        boost::tuple< boost::shared_ptr<std::ostream>, std::list<Ptr<L3AggregateTracer> > >
-            tracers = L3RateTracer::InstallAll ("aggregate-trace.txt", Seconds (1.0));
+        boost::tuple< boost::shared_ptr<std::ostream>, std::list<Ptr<ndn::L3AggregateTracer> > >
+          aggTracers = ndn::L3AggregateTracer::InstallAll ("aggregate-trace.txt", Seconds (1.0));
         
         Simulator::Run ();
+        
+        ...
 
 
 - :ndnsim:`ndn::L3RateTracer`
@@ -36,12 +44,19 @@
 
     .. code-block:: c++
 
+        // necessary includes
+	#include <ns3/ndnSIM/utils/tracers/ndn-l3-rate-tracer.h>
+
+	...        
+
         // the following should be put just before calling Simulator::Run in the scenario
 
-        boost::tuple< boost::shared_ptr<std::ostream>, std::list<Ptr<L3RateTracer> > >
-            tracers = L3RateTracer::InstallAll ("rate-trace.txt", Seconds (1.0));
+        boost::tuple< boost::shared_ptr<std::ostream>, std::list<Ptr<ndn::L3RateTracer> > >
+          rateTracers = ndn::L3RateTracer::InstallAll ("rate-trace.txt", Seconds (1.0));
         
         Simulator::Run ();
+        
+        ...
 
 
 .. note::
@@ -50,3 +65,7 @@
     Eventually, we will port most of them to the current code, but it is not our main priority at the moment and would really appreciate help with writing new tracers and porting the old ones. 
 
 
+Example
++++++++
+
+Please refer to the :ref:`this example <trace example>`.