diff --git a/src/sage/manifolds/differentiable/diff_form_module.py b/src/sage/manifolds/differentiable/diff_form_module.py
index 9aee83e2222..a3026864ffc 100644
--- a/src/sage/manifolds/differentiable/diff_form_module.py
+++ b/src/sage/manifolds/differentiable/diff_form_module.py
@@ -12,6 +12,8 @@
   (in practice, not parallelizable) differentiable manifold `M`
 - :class:`DiffFormFreeModule` for differential forms with values on a
   parallelizable manifold `M`
+  (the subclass :class:`VectorFieldDualFreeModule` implements the special
+  case of differential 1-forms on a parallelizable manifold `M`)
 
 AUTHORS:
 
@@ -575,6 +577,8 @@ class DiffFormFreeModule(ExtPowerDualFreeModule):
         is not parallelizable, the class :class:`DiffFormModule` must be used
         instead.
 
+    For the special case of `-forms, use the class :class:`VectorFieldDualFreeModule`.
+
     INPUT:
 
     - ``vector_field_module`` -- free module `\mathfrak{X}(U,\Phi)` of vector