Some of the oil will flow out of the bag and can be collected.

VOA: special.2009.09.29

The other lets water flow out.

VOA: special.2009.04.20

The researchers point out that gene flow between crops and their wild relatives is common and difficult to contain.

VOA: special.2009.10.27

But,once the fire is out, the well still needs to be covered,or capped, to stop the flow of oil.

VOA: special.2009.03.22

This makes it difficult for air to flow in and out of the lungs.

VOA: special.2009.07.28