21.   Ancient inhabitants may have built dikes, they say, and the structures could provide valuable clues about this early civilization.

22.   Anecdotal evidence provides conflicting clues, too.

23.   AOL will provide one clue to help identify each familiar voice you hear from your computer.

24.   Another device sent sound waves through the skin to make it reverberate like a drumhead, providing clues to delamination or changes in thickness.

25.   As they wade through the stalks, participants will collect puzzle pieces that will provide clues needed to navigate their way.

26.   As the study progresses, researchers and patient advocacy groups hope it might provide clues to help unravel the causes of this rare and mysterious illness.

27.   Authorities hoped the book would provide clues as to the identities of the remains found.

28.   A look at two key issues, energy and health care, may provide some clues.

29.   A program note can provide a clue, but more often than not the deliberately illogical can look merely arbitrary.

30.   A refined family tree will provide better clues on how the complex social behavior of ant colonies evolved.