21.   Astronomers know so little about it and its orbit that they cannot predict its exact location with the precision normally desired for such an encounter.

22.   At times, the border itself seems more illusory than real, with even the locals disagreeing on its exact location.

23.   Because the exact location of magnetic north has drifted over the years, they can use charts to figure out when the soil was last heated.

24.   Before the procedure is done, doctors inject a dye into the blood vessels and take x-rays that reveal the exact location, size and configuration of the aneurysm.

25.   A new technology called Arial View uses badges that emit infrared signals every two seconds to monitor electronically the exact location of employees.

26.   All the programs did a good job of finding addresses, but Expedia Streets seemed to be the best at pinpointing exact locations.

27.   BP said it will soon begin drilling nine appraisal and exploration wells to determine the extent and exact location of the reserves.

28.   But Matt Furman, an official with the National Transportation Safety Board, said that the plane had crashed, but that its exact location was not known.

29.   But the border is unmarked, and there has been a long-running dispute between Yugoslavia and Macedonia about its exact location.

30.   But the spokesman refused to give a more exact location of the search.