31.   But an underlying cause has been frustratingly elusive.

32.   But for treatment to be effective, the underlying cause needs to be clear.

33.   But either way, the underlying cause may be more fundamental.

34.   But it failed to address what many call the underlying causes of the deep divisions that have disabled the Security Council.

35.   But it warns that the underlying causes of the conflicts in these countries persist.

36.   But hypertension is a common ailment with many possible origins, so it can be difficult to parse out and treat the underlying cause.

37.   But she said she has reservations about the program, largely because she fears it fails to address the underlying causes of teen pregnancy.

38.   But that was merely the beginning of the crisis, not its underlying cause.

39.   But one underlying cause is the lucrative oil contracts Baghdad has been negotiating with many countries to take effect as soon as U.N. sanctions are lifted.

40.   But the underlying cause of heart disease has eluded its pursuers.