1.   Doctors do not know the exact cause of the disease.

2.   Linguists currently have little understanding of the exact cause of language change.

3.   Police are still investigating the exact cause of the accident.

4.   Rumours that he had been deliberately poisoned were generally discredited, but the exact cause of his death was never established.

5.   Surprisingly perhaps, linguists currently have little understanding of the exact causes of language change.

6.   The exact cause of death is still open to question.

7.   The exact cause of hypercalcemia in this disorder is poorly understood.

8.   The exact cause of the complaint has to be ascertained.

9.   The Staffordshire authorities are carrying out an inquest into the accident to establish the exact cause of death.