21.   Biochemical assay techniques have been used before to identify animal meat residues in cooking pots at archaeological sites.

22.   After each exercise, one group stretched the muscles just used before moving to the next machine.

23.   But because they start with products that have been used before, they often wind up with impurities like copper and tin that are not present in iron ore.

24.   But Bush is sure to counter that as a country we have overdeployed our forces and cannot protect them, a theme he has used before.

25.   But meta-analysis of tricyclic antidepressants, which were widely used before the advent of Prozac, found equivalent or higher rates of effectiveness.

26.   But on Sunday, Gore raised the issue in a chant he has used before when stumping for Democratic candidates around the country.

27.   But Postol and others describe the visit as a tactic they say the government has used before to silence informed dissidents with high-level security clearances.

28.   Double juries have been used before in Oklahoma, Wintory said, and have been successfully used in prosecuting members of the El Rukin gang in Chicago.

29.   Earlier in September I had rented a car with a Rockwell computer, a system I had used before.

30.   Drawings indicate it looked a lot like those massive steam engines that farmers used before gasoline tractors.