| Clue | Source | Date |
|---|---|---|
| Landscapes of 33 Acrosses etc | The Telegraph Cross Atlantic | 08 Jan 2025 |
| Limestone areas with sinkholes and caverns | New York Times | 22 May 2016 |
| Limestone areas with sinkholes and caverns | ||
| Rough limestone regions with sinkholes and caverns | ||
| Limestone regions with deep fissures and sinkholes |