11.   Scientists caution that more research is needed and that introducing transgenic mosquitoes into malaria-infected regions is years away.

12.   Scientists cautioned that the number of dead otters was probably higher because many animals that die sink at sea and their carcasses are never found.

13.   Scientists caution that emissions from rising energy use aggravate global warming.

14.   Scientists cautioned that the results are early and that many more tests are needed before an optimal treatment is found.

15.   Some scientists cautioned, however, that the conclusions have yet to be confirmed and that other interpretations of the evidence remain possible.

16.   Some scientists cautioned against reading a global warming scenario into the recent record-breaking string of winters.

17.   The scientists caution that the van der Waals explanation remains unproven.

18.   The scientists cautioned that no verification system can be perfect.

19.   The scientists caution that the findings are preliminary.

20.   Then scientists cautioned that estrogen might spur breast cancer.