1.   Most researchers doubt that there has ever been a strong direct correlation between Church policy and individual family planning Decisions.

2.   Both researchers doubt that any species could sustain such a mutation rate indefinitely.

3.   But many researchers doubt that effect can be reliably measured.

4.   But some researchers doubt that one-stop shopping is what customers want.

5.   But though such a drug might be useful as a diet aid, most researchers doubt it could cure obesity.

6.   In fact, some researchers doubt this vaccine is strong enough to be effective.

7.   Many researchers still doubt that leprosy occurs naturally in nonhuman primates.

8.   Most researchers doubt that anything could still be alive on Mars today.

9.   So the pitch to the general populace was usually smoother-flowing traffic, although some researchers doubt that rail reduces congestion very much.

10.   The trees stand like sentinels now on an otherwise bare nob, and they are so exposed that researchers doubt the murrelets will return.