diff --git a/lapack/testlapack/dlanst.go b/lapack/testlapack/dlanst.go
index e366811a..3aeb1f65 100644
--- a/lapack/testlapack/dlanst.go
+++ b/lapack/testlapack/dlanst.go
@@ -23,15 +23,19 @@ func DlanstTest(t *testing.T, impl Dlanster) {
 	for _, norm := range []lapack.MatrixNorm{lapack.MaxAbs, lapack.MaxColumnSum, lapack.MaxRowSum, lapack.Frobenius} {
 		for _, n := range []int{1, 3, 10, 100} {
 			for cas := 0; cas < 100; cas++ {
+				// Generate randomly the main diagonal of the
+				// symmetric tridiagonal matrix A.
 				d := make([]float64, n)
 				for i := range d {
 					d[i] = rnd.NormFloat64()
 				}
+				// Generate randomly the off-diagonal of A.
 				e := make([]float64, n-1)
 				for i := range e {
 					e[i] = rnd.NormFloat64()
 				}
 
+				// Create A in dense representation.
 				m := n
 				lda := n
 				a := make([]float64, m*lda)
@@ -42,8 +46,12 @@ func DlanstTest(t *testing.T, impl Dlanster) {
 					a[i*lda+i+1] = e[i]
 					a[(i+1)*lda+i] = e[i]
 				}
+
 				work := make([]float64, n)
+				// Compute a norm of A using Dlanst.
 				syNorm := impl.Dlanst(norm, n, d, e)
+				// Compute a reference value for the norm using
+				// Dlange and the dense representation of A.
 				geNorm := impl.Dlange(norm, m, n, a, lda, work)
 				if math.Abs(syNorm-geNorm) > 1e-12 {
 					t.Errorf("Norm mismatch: norm = %v, cas = %v, n = %v. Want %v, got %v.", string(norm), cas, n, geNorm, syNorm)