| Clue | Source | Date |
|---|---|---|
| Electromagnetic radiation rays | ||
| Some brothers, say | The New Yorker | 07 Oct 2019 |
| Deltas' preceders | Wall Street Journal | 28 May 2019 |
| Deltas' preceders | ||
| More Greek letters | Universal | 15 Dec 2017 |
| More Greek letters | ||
| Some Greek letters | Universal | 20 Feb 2015 |
| Some Greek letters | ||
| Ultrahigh-energy photons | ||
| Greek letters | ||
| Symbols of surface tension | ||
| Greek letters | ||
| Greek letters | ||
| Greek letters | ||
| Thirds in series | ||
| Third items in series | ||
| Followers of betas | ||
| Greek letters. |