| Answer | Crossword Clue |
|---|---|
| PSS | Additions to letters: Abbr. |
| PPS | Additions to letters |
| PSS | Additions to letters. |
| PSS | Endings to some letters: Abbr. |
| GPO | Where to find letters in boxes (abbr.) |
| GPO | Where to find letters in boxes: Abbr. |
| MSS | Contents of some letters to the editor: Abbr. |
