diff --git a/lib/colvars/colvar.cpp b/lib/colvars/colvar.cpp
index f6652852eb..e07ddbcc5d 100644
--- a/lib/colvars/colvar.cpp
+++ b/lib/colvars/colvar.cpp
@@ -969,16 +969,20 @@ cvm::real colvar::update()
   if (tasks[task_extended_lagrangian]) {
 
     cvm::real dt = cvm::dt();
+    cvm::real f_ext;
 
     // the total force is applied to the fictitious mass, while the
     // atoms only feel the harmonic force
-    // fr: extended coordinate force; f: colvar force applied to atomic coordinates
-    fr   = f;
-    fr  += (-0.5 * ext_force_k) * this->dist2_lgrad (xr, x);
-    f    = (-0.5 * ext_force_k) * this->dist2_rgrad (xr, x);
+    // fr: extended coordinate force (without harmonic spring), for output in trajectory
+    // f_ext: total force on extended coordinate (including harmonic spring)
+    // f: - initially, external biasing force
+    //    -  after this code block, colvar force to be applied to atomic coordinates, ie. spring force
+    fr    = f;
+    f_ext = f + (-0.5 * ext_force_k) * this->dist2_lgrad (xr, x);
+    f     =     (-0.5 * ext_force_k) * this->dist2_rgrad (xr, x);
 
-    // leap frog: starting from x_i, f_i, v_(i-1/2)
-    vr  += (0.5 * dt) * fr / ext_mass;
+    // leapfrog: starting from x_i, f_i, v_(i-1/2)
+    vr  += (0.5 * dt) * f_ext / ext_mass;
     // Because of leapfrog, kinetic energy at time i is approximate
     kinetic_energy = 0.5 * ext_mass * vr * vr;
     potential_energy = 0.5 * ext_force_k * this->dist2(xr, x);
@@ -987,7 +991,7 @@ cvm::real colvar::update()
       vr -= dt * ext_gamma * vr.real_value;
       vr += dt * ext_sigma * cvm::rand_gaussian() / ext_mass;
     }
-    vr  += (0.5 * dt) * fr / ext_mass;
+    vr  += (0.5 * dt) * f_ext / ext_mass;
     xr  += dt * vr;
     xr.apply_constraints();
     if (this->b_periodic) this->wrap (xr);
@@ -1216,15 +1220,8 @@ std::istream & colvar::read_traj (std::istream &is)
   }
 
   if (tasks[task_output_system_force]) {
-
     is >> ft;
-
-    if (tasks[task_extended_lagrangian]) {
-      is >> fr;
-      ft_reported = fr;
-    } else {
-      ft_reported = ft;
-    }
+    ft_reported = ft;
   }
 
   if (tasks[task_output_applied_force]) {
@@ -1282,7 +1279,7 @@ std::ostream & colvar::write_traj_label (std::ostream & os)
        << cvm::wrap_string (this->name, this_cv_width);
 
     if (tasks[task_extended_lagrangian]) {
-      // restraint center
+      // extended DOF
       os << " r_"
          << cvm::wrap_string (this->name, this_cv_width-2);
     }
@@ -1294,29 +1291,22 @@ std::ostream & colvar::write_traj_label (std::ostream & os)
        << cvm::wrap_string (this->name, this_cv_width-2);
 
     if (tasks[task_extended_lagrangian]) {
-      // restraint center
+      // extended DOF
       os << " vr_"
          << cvm::wrap_string (this->name, this_cv_width-3);
     }
   }
 
   if (tasks[task_output_energy]) {
-      os << " Ep_"
-         << cvm::wrap_string (this->name, this_cv_width-3)
-         << " Ek_"
-         << cvm::wrap_string (this->name, this_cv_width-3);
+    os << " Ep_"
+       << cvm::wrap_string (this->name, this_cv_width-3)
+       << " Ek_"
+       << cvm::wrap_string (this->name, this_cv_width-3);
   }
 
   if (tasks[task_output_system_force]) {
-
     os << " fs_"
        << cvm::wrap_string (this->name, this_cv_width-3);
-
-    if (tasks[task_extended_lagrangian]) {
-      // restraint center
-      os << " fr_"
-         << cvm::wrap_string (this->name, this_cv_width-3);
-    }
   }
 
   if (tasks[task_output_applied_force]) {
@@ -1359,31 +1349,30 @@ std::ostream & colvar::write_traj (std::ostream &os)
   }
 
   if (tasks[task_output_energy]) {
-      os << " "
-         << std::setprecision (cvm::cv_prec) << std::setw (cvm::cv_width)
-         << potential_energy
-         << " "
-         << kinetic_energy;
+    os << " "
+       << std::setprecision (cvm::cv_prec) << std::setw (cvm::cv_width)
+       << potential_energy
+       << " "
+       << kinetic_energy;
   }
 
 
   if (tasks[task_output_system_force]) {
-
-    if (tasks[task_extended_lagrangian]) {
-      os << " "
-         << std::setprecision (cvm::cv_prec) << std::setw (cvm::cv_width)
-         << ft;
-    }
-
     os << " "
        << std::setprecision (cvm::cv_prec) << std::setw (cvm::cv_width)
        << ft_reported;
   }
 
   if (tasks[task_output_applied_force]) {
-    os << " "
-       << std::setprecision (cvm::cv_prec) << std::setw (cvm::cv_width)
-       << f;
+    if (tasks[task_extended_lagrangian]) {
+      os << " "
+         << std::setprecision (cvm::cv_prec) << std::setw (cvm::cv_width)
+         << fr;
+    } else {
+      os << " "
+         << std::setprecision (cvm::cv_prec) << std::setw (cvm::cv_width)
+         << f;
+    }
   }
 
   return os;
diff --git a/lib/colvars/colvarbias.cpp b/lib/colvars/colvarbias.cpp
index 58ec049b3c..993cb3cd59 100644
--- a/lib/colvars/colvarbias.cpp
+++ b/lib/colvars/colvarbias.cpp
@@ -31,7 +31,7 @@ colvarbias::colvarbias (std::string const &conf, char const *key)
        bi++) {
     if ((*bi)->name == this->name)
       cvm::fatal_error ("Error: this bias cannot have the same name, \""+this->name+
-                        "\", of another bias.\n");
+                        "\", as another bias.\n");
   }
 
   // lookup the associated colvars
diff --git a/lib/colvars/colvarbias_meta.cpp b/lib/colvars/colvarbias_meta.cpp
index 3ddc6af6c5..8e8650e730 100644
--- a/lib/colvars/colvarbias_meta.cpp
+++ b/lib/colvars/colvarbias_meta.cpp
@@ -37,8 +37,7 @@ colvarbias_meta::colvarbias_meta (std::string const &conf, char const *key)
     new_hills_begin (hills.end())
 {
   if (cvm::n_abf_biases > 0)
-    cvm::log ("Warning: ABF and metadynamics running at the "
-              "same time can lead to inconsistent results.\n");
+    cvm::log ("Warning: running ABF and metadynamics together is not recommended unless applyBias is off for ABF.\n");
 
   get_keyval (conf, "hillWeight", hill_weight, 0.01);
   if (hill_weight == 0.0)
diff --git a/lib/colvars/colvargrid.h b/lib/colvars/colvargrid.h
index ccaf046039..fd2365da45 100644
--- a/lib/colvars/colvargrid.h
+++ b/lib/colvars/colvargrid.h
@@ -661,7 +661,7 @@ public:
 
 
   /// \brief Check that the grid information inside (boundaries,
-  /// widths, ...) is consistent with the one of another grid
+  /// widths, ...) is consistent with that of another grid
   void check_consistency (colvar_grid<T> const &other_grid)
   {
     for (size_t i = 0; i < nd; i++) {
diff --git a/lib/colvars/colvarmodule.cpp b/lib/colvars/colvarmodule.cpp
index b6f57c16c2..122cd01a5f 100644
--- a/lib/colvars/colvarmodule.cpp
+++ b/lib/colvars/colvarmodule.cpp
@@ -1069,7 +1069,7 @@ cvm::quaternion::position_derivative_inner (cvm::rvector const &pos,
 
 
 // Calculate the optimal rotation between two groups, and implement it
-// as a quaternion.  The method is the one documented in: Coutsias EA,
+// as a quaternion.  Uses the method documented in: Coutsias EA,
 // Seok C, Dill KA.  Using quaternions to calculate RMSD.  J Comput
 // Chem. 25(15):1849-57 (2004) DOI: 10.1002/jcc.20110 PubMed: 15376254
 
diff --git a/lib/colvars/colvarmodule.h b/lib/colvars/colvarmodule.h
index 2146b2cb94..47af4822c6 100644
--- a/lib/colvars/colvarmodule.h
+++ b/lib/colvars/colvarmodule.h
@@ -2,7 +2,7 @@
 #define COLVARMODULE_H
 
 #ifndef COLVARS_VERSION
-#define COLVARS_VERSION "2013-10-22"
+#define COLVARS_VERSION "2013-12-13"
 #endif
 
 #ifndef COLVARS_DEBUG
diff --git a/lib/colvars/colvartypes.h b/lib/colvars/colvartypes.h
index 4c285631a8..011f22cbdf 100644
--- a/lib/colvars/colvartypes.h
+++ b/lib/colvars/colvartypes.h
@@ -833,7 +833,7 @@ public:
   }
 
   /// Gradient of the square distance: returns a 4-vector equivalent
-  /// to the one provided by slerp
+  /// to that provided by slerp
   inline cvm::quaternion dist2_grad (cvm::quaternion const &Q2) const
   {
     cvm::real const cos_omega = this->q0*Q2.q0 + this->q1*Q2.q1 + this->q2*Q2.q2 + this->q3*Q2.q3;