| Clue | Source | Date |
|---|---|---|
| Image file suffix | LA Times Daily | 16 Nov 2020 |
| Image file suffix | The Washington Post | 16 Nov 2020 |
| Image file format | Universal | 22 Jul 2020 |
| Image file extension | New York Times | 06 Jan 2019 |
| Image file extension | ||
| Extension on image-file names | The Chronicle of Higher Education | 23 Jan 2015 |
| Extension on image-file names | ||
| File format for some pics |