A major contribution to the new and more sophisticated picture was made by American researchers.

The tractors were left at the pole for the use of American researchers.

American researchers are excited by the operation, but confused about exactly how it works.

American researchers were able to study and process some of this foreign data.

American researchers questioned the findings, which do not match results in this country.

This view has the support of an American researcher as well.

The book was written by one of the leading American researchers in the field of education.

More than 200 international volunteers have worked at the site, in addition to American researchers and students.

But many American researchers clearly feel that they are slipping.

Some American researchers apparently made a similar discovery at around the same time.