diff --git a/src/core/examples/main-callback.cc b/src/core/examples/main-callback.cc
index 06bd5a8b6..519db657a 100644
--- a/src/core/examples/main-callback.cc
+++ b/src/core/examples/main-callback.cc
@@ -21,17 +21,39 @@
 #include "ns3/assert.h"
 #include <iostream>
 
+/**
+ * \file
+ * \ingroup callback
+ * Example program illustrating use of callback functions and methods.
+ *
+ * See \ref callback
+ */
+
 using namespace ns3;
 
-static double 
+/**
+ * Example Callback function.
+ *
+ * \param [in] a The first argument.
+ * \param [in] b The second argument.
+ * \returns The first argument.
+ */
+static double
 CbOne (double a, double b)
 {
   std::cout << "invoke cbOne a=" << a << ", b=" << b << std::endl;
   return a;
 }
 
+/** Example Callback class. */
 class MyCb {
 public:
+  /**
+   * Example Callback class method.
+   *
+   * \param [in] a The argument.
+   * \returns -5
+   */
   int CbTwo (double a) {
     std::cout << "invoke cbTwo a=" << a << std::endl;
     return -5;
diff --git a/src/core/examples/main-test-sync.cc b/src/core/examples/main-test-sync.cc
index 1cb591ace..5aa120eed 100644
--- a/src/core/examples/main-test-sync.cc
+++ b/src/core/examples/main-test-sync.cc
@@ -29,12 +29,23 @@
 #include <unistd.h>
 #include <sys/time.h>
 
+/**
+ * \file
+ * \ingroup scheduler
+ * An example of scheduling events in a background thread.
+ *
+ * See \ref ns3::SystemThread,
+ * \ref ns3::SimulatorImpl::ScheduleWithContext
+ */
+
 using namespace ns3;
 
 NS_LOG_COMPONENT_DEFINE ("TestSync");
 
+/** Check that the event functions run in the intended order. */
 bool gFirstRun = false;
 
+/** An event method called many times from the background thread. */
 void 
 inserted_function (void)
 {
@@ -43,6 +54,7 @@ inserted_function (void)
                  Simulator::Now ().GetSeconds () << " s");
 }
 
+/** An event method called many times from the main thread. */
 void 
 background_function (void)
 {
@@ -51,6 +63,7 @@ background_function (void)
                  Simulator::Now ().GetSeconds () << " s");
 }
 
+/** An event method called once from the main thread. */
 void 
 first_function (void)
 {
@@ -59,10 +72,13 @@ first_function (void)
   gFirstRun = true;
 }
 
+/** Example class with a method for the background task. */
 class FakeNetDevice
 {
 public:
+  /** Constructor. */
   FakeNetDevice ();
+  /** The thread entry point. */
   void Doit3 (void);
 };
 
@@ -86,7 +102,15 @@ FakeNetDevice::Doit3 (void)
     }
 }
 
-
+/**
+ * Example use of ns3::SystemThread.
+ *
+ * This example is a complete simulation.
+ * It schedules \c first_function and many executions of \c background_function
+ * to execute in the main (foreground) thread.  It also launches a background
+ * thread with an instance of FakeNetDevice, which schedules many instances of
+ * \c inserted_function.
+ */
 void 
 test (void)
 {
diff --git a/src/core/examples/sample-simulator.cc b/src/core/examples/sample-simulator.cc
index 4accc4b45..925dd2cd3 100644
--- a/src/core/examples/sample-simulator.cc
+++ b/src/core/examples/sample-simulator.cc
@@ -25,6 +25,12 @@
 #include "ns3/double.h"
 #include "ns3/random-variable-stream.h"
 
+/**
+ * \file
+ * \ingroup simulator
+ * Example program demonstrating use of various Schedule functions.
+ */
+
 using namespace ns3;
 
 class MyModel
diff --git a/src/core/model/command-line.h b/src/core/model/command-line.h
index aa81586b5..888f29263 100644
--- a/src/core/model/command-line.h
+++ b/src/core/model/command-line.h
@@ -436,7 +436,7 @@ private:
 
 
 /** \ingroup commandline
- *  \defgroup commandlinehelper Helpers to Specialize on \c bool
+ *  \defgroup commandlinehelper Helpers to Specialize on bool
  */
 /**
  * \ingroup commandlinehelper
diff --git a/src/core/model/int64x64-128.h b/src/core/model/int64x64-128.h
index d935f60a6..aa2a24573 100644
--- a/src/core/model/int64x64-128.h
+++ b/src/core/model/int64x64-128.h
@@ -79,12 +79,12 @@ public:
   /// Default constructor.
   inline int64x64_t ()
     : _v (0)  {}
-  /**@{*/
   /**
-   * Construct from a floating point value.
+   * \name Construct from a floating point value.
    *
    * \param [in] value Floating value to represent.
    */
+  /**@{*/
   inline int64x64_t (const double value)
   {
     const int64x64_t tmp ((long double)value);
@@ -120,12 +120,12 @@ public:
   }
   /**@}*/
 
-  /**@{*/
   /**
-   * Construct from an integral type.
+   * \name Construct from an integral type.
    *
    * \param [in] v Integer value to represent.
    */
+  /**@{*/
   inline int64x64_t (const int v)
     : _v (v)
   {
@@ -157,6 +157,7 @@ public:
     _v <<= 64;
   }
   /**@}*/
+  
   /**
    * Construct from explicit high and low values.
    *
diff --git a/src/core/model/log.cc b/src/core/model/log.cc
index 46d537567..39ffdccb5 100644
--- a/src/core/model/log.cc
+++ b/src/core/model/log.cc
@@ -46,6 +46,7 @@ namespace ns3 {
 /**
  * \ingroup logging
  * The LogTimePrinter.
+ * This is private to the logging implementation.
  */
 static LogTimePrinter g_logTimePrinter = 0;
 /**
@@ -58,6 +59,7 @@ static LogNodePrinter g_logNodePrinter = 0;
  * \ingroup logging
  * Handler for \c print-list token in NS_LOG
  * to print the list of log components.
+ * This is private to the logging implementation.
  */
 class PrintList
 {
@@ -65,7 +67,10 @@ public:
   PrintList ();  //<! Constructor, prints the list and exits.
 };
 
-/** Invoke handler for \c print-list in NS_LOG environment variable. */
+/**
+ * Invoke handler for \c print-list in NS_LOG environment variable.
+ * This is private to the logging implementation.
+ */
 static PrintList g_printList;
 
   
@@ -479,7 +484,9 @@ LogComponentPrintList (void)
 }
 
 /**
+ * \ingroup
  * Check if a log component exists.
+ * This is private to the logging implementation.
  *
  * \param componentName The putative log component name.
  * \returns \c true if \c componentName exists.
@@ -505,6 +512,7 @@ static bool ComponentExists(std::string componentName)
 
 /**
  * Parse the \c NS_LOG environment variable.
+ * This is private to the logging implementation.
  */
 static void CheckEnvironmentVariables (void)
 {
diff --git a/src/core/model/nstime.h b/src/core/model/nstime.h
index 33768a3d3..1f53235c1 100644
--- a/src/core/model/nstime.h
+++ b/src/core/model/nstime.h
@@ -145,9 +145,13 @@ public:
 	Mark (this);
       }
   }
+  /**
+   * \name Numeric constructors.
+   *  Construct from a numeric value.
+   * @{
+   */
   /**
    *  Construct from a numeric value.
-   *
    *  The current time resolution will be assumed as the unit.
    *  \param [in] v The value.
    *  @{
@@ -217,6 +221,7 @@ public:
       }
   }
   /**@}*/
+  /**@}*/
   
   /**
    * \brief Construct Time object from common time expressions like "1ms"
@@ -803,7 +808,7 @@ std::istream & operator >> (std::istream & is, Time & time);
 
 /**
  * \ingroup time
- * \defgroup timecivil Standard time units.
+ * \defgroup timecivil Standard Time Units.
  * \brief Convenience constructors in standard units.
  *
  * For example:
@@ -913,19 +918,8 @@ inline Time TimeStep (uint64_t ts)
   return Time (ts);
 }
 
-/**
- * \ingroup time
- * \class ns3::TimeValue
- * \brief Attribute for objects of type ns3::Time
- */
 ATTRIBUTE_VALUE_DEFINE (Time);
-
-/**
- *  Attribute accessor function for Time
- *  @{
- */
 ATTRIBUTE_ACCESSOR_DEFINE (Time);
-/**@}*/
 
 /**
  *  \ingroup time
diff --git a/src/core/model/object-factory.h b/src/core/model/object-factory.h
index 4173bfe4d..c16efde4f 100644
--- a/src/core/model/object-factory.h
+++ b/src/core/model/object-factory.h
@@ -61,12 +61,12 @@ public:
    */
   ObjectFactory (std::string typeId);
 
+  /**@{*/
   /**
    * Set the TypeId of the Objects to be created by this factory.
    *
    * \param tid The TypeId of the object to instantiate.
    */
-  /**@{*/
   void SetTypeId (TypeId tid);
   void SetTypeId (const char *tid);
   void SetTypeId (std::string tid);
@@ -184,6 +184,11 @@ ATTRIBUTE_HELPER_HEADER (ObjectFactory);
 
 } // namespace ns3
 
+
+/***************************************************************
+ *  Implementation of the templates declared above.
+ ***************************************************************/
+
 namespace ns3 {
 
 template <typename T>
diff --git a/src/core/model/object.cc b/src/core/model/object.cc
index 8de97d1a6..1fbad4235 100644
--- a/src/core/model/object.cc
+++ b/src/core/model/object.cc
@@ -22,7 +22,6 @@
 #include "object.h"
 #include "object-factory.h"
 #include "assert.h"
-#include "singleton.h"
 #include "attribute.h"
 #include "log.h"
 #include "string.h"