Two recent studies cast doubt that the effect can be achieved in larger mammals.

Recent studies cast doubt on such a causal relation, and so more empirical data is required.

But a new study has cast doubt on the amount of transfers - $16.6 billion last year - that actually goes to families.

Another study has also cast doubt on the effectiveness of e-mail for getting a message through to government.

Several studies cast doubts on the nature of the dwarf galaxy.

However, other studies cast doubt on the efficacy of involuntary treatment.

However, some later studies cast doubt on this paradigm.

But rigorous studies in recent years have cast doubt on some of the benefits that many women and their doctors took for granted.

But recent studies have cast doubt on this assertion.

Since then various studies have cast doubt on this belief.