So energy expert Eric Potter says it is too early to know how the new gas shale reserves will affect the market.

VOA: special.2009.10.23

He said the Earth is like a large mechanical device that will survive only if people living on it know how to operate it correctly.

VOA: special.2010.05.30

Jeffrey Olson says experts do not know what will take the place of the plants and animals that are lost, or how wildlife will survive in a changed environment.

VOA: special.2009.09.28

We are worried because we do not know how long they will stay or how we will take care of them.

VOA: standard.2009.10.27

Otherwise,he warns, the great Iranian nation which has developed its own nuclear technology will produce the fuel by using its own know-how.

VOA: standard.2009.11.28

Colin Macpherson, a professor of Earth sciences at Britain's Durham University, says it's impossible to know how long the volcano will continue to erupt.

VOA: standard.2010.04.16

so we will know how we are really doing when we treat this condition,"

VOA: standard.2010.01.01

He says it is difficult to know how the disease will evolve.

VOA: standard.2009.05.14