| 1 | I have decided not to pursue (ie investigate) the matter any further. | |
| 2 | They tried to trace the rumour to its source. | |
| 3 | It took the police several days to track down their quarry. | |
| 4 | The accident can be traced to various causes. | |
| 5 | The new measurements will also help scientists track how much the glacier is melting from year to year. |