| Clue | Source | Date |
|---|---|---|
| Challenging poser...that rows 3, 5, 11 and 13 have broken | Wall Street Journal | 23 Sep 2021 |
| Poser | Newsday | 02 Aug 2017 |
| Formidable problem | Wall Street Journal | 06 Apr 2016 |
| One who's not easily convinced | ||
| Heck of a puzzle | ||
| Baffling problem | ||
| It's pretty challenging | ||
| Baffler | ||
| Poser | ||
| Difficulty | ||
| Poser | ||
| Difficult task | ||
| Difficult task | ||
| Hard problem | ||
| Squirrel's headache? |