21.   But he declined to be specific about what problems persist.

22.   But problems persisted, including the lack of a certificate and other uncorrected violations.

23.   But one problem persists.

24.   But problems persist in the Andean countries, McCoy said.

25.   But the Iraq problem persists.

26.   But serious problems persist.

27.   But the overheating problem persisted when they tried to use it in animal studies.

28.   But the mayor acknowledged that other problems persist.

29.   But the problem persists.