"There's a lot of possible factors at work that we have to look into," he said.

But there were other possible factors: * Their commercial enterprises.

It is also important to understand the possible contributing factors.

Among possible factors, drought has been thought by many experts to have played a role.

But the survey did not ask for information about other possible factors, like diet.

Another possible factor, one equally difficult to measure, is the effect of the new tax laws.

The list of possible factors is both long and confounded with one another.

Finally, another possible factor is that some countries are again trying to get something through which they tried to do before without success.

Other possible factors include less access to health care facilities and treatment.

He suggested still another possible factor, on the chemical level.