It is expected that teachers will have to prove their ability in eight areas - but the most contentious is reported to be the measurement of pupils' improvement.

BBC: Pay dispute over pupil improvement

The individual soldier, sailor, Marine, airman prove their own ability, and we've have women, particularly in the medical field, that have done these various things.

NPR: Women in Combat: Rules and Reality

These emerging solutions will have to prove to the industry their ability to scale over time.

FORBES: Brand Impact Online: New Thinking Inside The Box

Carrier is well-known among distance runners for trying to run down a herd of antelope a few years ago to prove that humans were built to run great distances, their survival dependent on their ability to persistence hunt.

CNN: Running debate: Bare or in shoes?

Tapping taxpayers - when the banks are so unpopular - would prove politically hard to sell and the banks are warning that if they boost their capital it will dent their ability to lend.

BBC: Deadlock in the eurozone