| Clue | Source | Date |
|---|---|---|
| Oceanographers' charts | ||
| Nautical navigation aids | New York Times | 22 Jun 2024 |
| Nautical charts | The Washington Post Sunday | 23 Jan 2022 |
| Charts for sailors | Universal | 14 Jul 2021 |
| Navigator's charts | Wall Street Journal | 02 Dec 2017 |
| Nautical charts | Eugene Sheffer | 23 Jan 2016 |
| Oceanographers' references | ||
| Oceanographic charts |