diff --git a/opm/core/transport/reorder/TransportModelTracerTof.cpp b/opm/core/transport/reorder/TransportModelTracerTof.cpp
index 70c2fc400..8d93f2480 100644
--- a/opm/core/transport/reorder/TransportModelTracerTof.cpp
+++ b/opm/core/transport/reorder/TransportModelTracerTof.cpp
@@ -38,10 +38,12 @@ namespace Opm
 
 
 
-    /// Solve for time-of-flight at next timestep.
+    /// Solve for time-of-flight.
     /// \param[in]  darcyflux         Array of signed face fluxes.
     /// \param[in]  porevolume        Array of pore volumes.
-    /// \param[in]  source            Transport source term.
+    /// \param[in]  source            Source term. Sign convention is:
+    ///                                 (+) inflow flux,
+    ///                                 (-) outflow flux.
     /// \param[out] tof               Array of time-of-flight values.
     void TransportModelTracerTof::solveTof(const double* darcyflux,
                                            const double* porevolume,
diff --git a/opm/core/transport/reorder/TransportModelTracerTof.hpp b/opm/core/transport/reorder/TransportModelTracerTof.hpp
index 21375d895..270ac328a 100644
--- a/opm/core/transport/reorder/TransportModelTracerTof.hpp
+++ b/opm/core/transport/reorder/TransportModelTracerTof.hpp
@@ -31,7 +31,13 @@ namespace Opm
 
     class IncompPropertiesInterface;
 
-    /// Implements a reordering transport solver for incompressible two-phase flow.
+    /// Implements a first-order finite volume solver for
+    /// (single-phase) time-of-flight using reordering.
+    /// The equation solved is:
+    ///     v \cdot \grad\tau = \phi
+    /// where v is the fluid velocity, \tau is time-of-flight and
+    /// \phi is the porosity. This is a boundary value problem, where
+    /// \tau is specified to be zero on all inflow boundaries.
     class TransportModelTracerTof : public TransportModelInterface
     {
     public:
@@ -39,10 +45,12 @@ namespace Opm
         /// \param[in] grid      A 2d or 3d grid.
         TransportModelTracerTof(const UnstructuredGrid& grid);
 
-        /// Solve for time-of-flight at next timestep.
+        /// Solve for time-of-flight.
         /// \param[in]  darcyflux         Array of signed face fluxes.
         /// \param[in]  porevolume        Array of pore volumes.
-        /// \param[in]  source            Transport source term.
+        /// \param[in]  source            Source term. Sign convention is:
+        ///                                 (+) inflow flux,
+        ///                                 (-) outflow flux.
         /// \param[out] tof               Array of time-of-flight values.
         void solveTof(const double* darcyflux,
                       const double* porevolume,
diff --git a/opm/core/transport/reorder/TransportModelTracerTofDiscGal.cpp b/opm/core/transport/reorder/TransportModelTracerTofDiscGal.cpp
index e9e812ef3..4bc2f1efb 100644
--- a/opm/core/transport/reorder/TransportModelTracerTofDiscGal.cpp
+++ b/opm/core/transport/reorder/TransportModelTracerTofDiscGal.cpp
@@ -446,10 +446,12 @@ namespace Opm
 
 
 
-    /// Solve for time-of-flight at next timestep.
+    /// Solve for time-of-flight.
     /// \param[in]  darcyflux         Array of signed face fluxes.
     /// \param[in]  porevolume        Array of pore volumes.
-    /// \param[in]  source            Transport source term.
+    /// \param[in]  source            Source term. Sign convention is:
+    ///                                 (+) inflow flux,
+    ///                                 (-) outflow flux.
     /// \param[in]  degree            Polynomial degree of DG basis functions used.
     /// \param[out] tof_coeff         Array of time-of-flight solution coefficients.
     ///                               The values are ordered by cell, meaning that
@@ -633,7 +635,20 @@ namespace Opm
         MAT_SIZE_T info = 0;
         dgesv_(&n, &nrhs, &jac_[0], &lda, &piv[0], &rhs_[0], &ldb, &info);
         if (info != 0) {
-            THROW("Lapack error: " << info);
+            // Print the local matrix and rhs.
+            std::cerr << "Failed solving single-cell system Ax = b in cell " << cell
+                      << " with A = \n";
+            for (int row = 0; row < n; ++row) {
+                for (int col = 0; col < n; ++col) {
+                    std::cerr << "    " << jac_[row + n*col];
+                }
+                std::cerr << '\n';
+            }
+            std::cerr << "and b = \n";
+            for (int row = 0; row < n; ++row) {
+                std::cerr << "    " << rhs_[row] << '\n';
+            }
+            THROW("Lapack error: " << info << " encountered in cell " << cell);
         }
         // The solution ends up in rhs_, so we must copy it.
         std::copy(rhs_.begin(), rhs_.end(), tof_coeff_ + num_basis*cell);
diff --git a/opm/core/transport/reorder/TransportModelTracerTofDiscGal.hpp b/opm/core/transport/reorder/TransportModelTracerTofDiscGal.hpp
index b9163f8ed..0285e1f02 100644
--- a/opm/core/transport/reorder/TransportModelTracerTofDiscGal.hpp
+++ b/opm/core/transport/reorder/TransportModelTracerTofDiscGal.hpp
@@ -31,7 +31,15 @@ namespace Opm
 
     class IncompPropertiesInterface;
 
-    /// Implements a reordering transport solver for incompressible two-phase flow.
+    /// Implements a discontinuous Galerkin solver for
+    /// (single-phase) time-of-flight using reordering.
+    /// The equation solved is:
+    ///     v \cdot \grad\tau = \phi
+    /// where v is the fluid velocity, \tau is time-of-flight and
+    /// \phi is the porosity. This is a boundary value problem, where
+    /// \tau is specified to be zero on all inflow boundaries.
+    /// The user may specify the polynomial degree of the basis function space
+    /// used, but only degrees 0 and 1 are supported so far.
     class TransportModelTracerTofDiscGal : public TransportModelInterface
     {
     public:
@@ -39,10 +47,13 @@ namespace Opm
         /// \param[in] grid      A 2d or 3d grid.
         TransportModelTracerTofDiscGal(const UnstructuredGrid& grid);
 
-        /// Solve for time-of-flight at next timestep.
+
+        /// Solve for time-of-flight.
         /// \param[in]  darcyflux         Array of signed face fluxes.
         /// \param[in]  porevolume        Array of pore volumes.
-        /// \param[in]  source            Transport source term.
+        /// \param[in]  source            Source term. Sign convention is:
+        ///                                 (+) inflow flux,
+        ///                                 (-) outflow flux.
         /// \param[in]  degree            Polynomial degree of DG basis functions used.
         /// \param[out] tof_coeff         Array of time-of-flight solution coefficients.
         ///                               The values are ordered by cell, meaning that