The practice is not unknown in some education action zones - such as Slough - and between small rural schools.

BBC: Share-a-teacher idea in staffing crisis

An additional unknown is what course of action the U.S. will take once Castro dies.

FORBES: Congress Looks At Cuba

Neeson followed that up with more small action hits like Unknown and The Grey.

FORBES: Liam Neeson: Hollywood's Most Reliable Action Star

We will continue to remind the leaders of Iraq that the country will slide into a dangerous unknown if they do not take immediate action.

CNN: Bombings, shooting leave at least 10 dead in Iraq

What course of action Congress will take is unknown.

FORBES: Magazine Article

Smart action in the face of the unknown is better than arrested progress due to more debate.

FORBES: Move up http://i.forbesimg.com t Move down

It is unknown whether the SEC may have declined to take further action as a result of a determination that no wrongdoing had occurred, insufficient evidence or for some other undisclosed reason.

FORBES: Gerova Financial Unit's Assets Were Questioned In SEC Wells Notice

Israel, itself the possessor of a nuclear arsenal of unknown size, is also watching closely and is quite capable of taking unilateral action if it feels threatened as the destruction of the Iraqi reactor in 1981 showed.

BBC: Nuclear threat casts global shadow