| Answer | Crossword Clue |
|---|---|
| PRESSES | Sine qua non, for newspapers. |
| INDEX | Sine qua non for a textbook. |
| FOURHANDS | Sine qua non for certain duets |
| TRAPEZE | Sine qua non for an aerialist. |
| VIGOR | Sine qua non for an athlete |
| PETROLEUM | Sine qua non for the wheels of industry. |
