21.   His only problem was keeping a lively staff of elves happy in the middle of frozen nowhere.

22.   His only problems are keeping his thank-yous fresh and his white dinner jacket clean.

23.   His biggest problem will be keeping his prestige with the demands on his time.

24.   If the same problems keep recurring time after time, he is going to have to make a painful judgment.

25.   In the end, Heche says, she had so good a time that her biggest problem was keeping a straight face.

26.   It was thought he was finally ready to play last week, but a nagging groin problem kept him on the practice field.

27.   Less serious problems kept cropping up throughout the day.

28.   Liquidity problems keep smaller companies from listing on German stock exchanges.

29.   Losses in gasoline were limited by speculation that refinery problems elsewhere could keep supplies low.

30.   Murphy said the biggest problem will be keeping purses high enough to attract high-quality horses that bettors will want to wager on.