| 1. | "His was an impenetrable darkness. - from Heart of Darkness by Joseph Conrad |
| 2. | How can I pierce the impenetrable blank of the futur. - from Leaves of Grass by Walt Whitman |
| 3. | An empty stream, a great silence, an impenetrable forest. - from Heart of Darkness by Joseph Conrad |
| 4. | She felt herself clad in an impenetrable armor of falsehood. - from Anna Karenina by Leo Tolstoy |
| 5. | But for me, in my impenetrable mantle, the safety was complete. - from Dr. Jekyll and Mr. Hyde by Robert Louis Stevenson |
| 6. | His fears were vain impenetrable charm. - from The Iliad of Homer by Homer |
| 7. | The enigma was more impenetrable than ever. - from Les Miserables by Victor Hugo |
| 8. | "No, I can't argue with them," he thought "they wear impenetrable armor, while I'm naked.. - from Anna Karenina by Leo Tolstoy |
| 9. | Farther back within the domain, the vision is impeded by an impenetrable screen of foliage. - from The Works of Edgar Allan Poe by Edgar Allan Poe |