If the bail-outs work, it will be hard to prove conclusively that they were needed.

ECONOMIST: The treasury secretary is torn between politics and policy

This type of study can't prove conclusively that NSAIDs are responsible for the lower risk of breast cancer.

CNN: Study: Aspirin, ibuprofen may cut breast cancer risk

It will never be possible to conclusively prove what advantages selected for longer necked giraffes, say the researchers.

BBC: Earth News

Most studies haven't been able to conclusively prove that antioxidants affect therapy.

CNN: Antioxidants may interfere with breast cancer treatment

The floods of the past few weeks, though bringing misery to many, prove only one thing conclusively.

BBC: News Online