| Clue | Source | Date |
|---|---|---|
| Power source that won’t work in the forest | Wall Street Journal | 15 Aug 2019 |
| Power source that won't work in the forest | ||
| *Device that supplies electricity outdoors | The Washington Post Sunday | 24 Dec 2017 |
| Green power source (with a tree) | Newsday | 29 Apr 2016 |