| Clue | Source | Date |
|---|---|---|
| Distilled coal product used to preserve wood | New York Times | 24 Jan 2023 |
| Coal product | Newsday | 07 Oct 2018 |
| Distilled coal product | Wall Street Journal | 13 Sep 2016 |
| Distilled coal product | New York Times | 01 Nov 2015 |
| Distilled coal product | ||
| Boat-deck application | ||
| Coal or pine product | ||
| Distilled pine product | ||
| Coal product | ||
| Coal or pine product | ||
| Coal or pine product |