The World Health Organization, the United Nations health agency, uses a system of six phases to warn of possible influenza pandemics.

VOA: special.2009.05.06

The bus uses a hybrid system that combines the hydrogen fuel cells with high power batteries.

VOA: special.2009.09.07

The process uses a closed system to keep hair and dirt out of the milk.

VOA: special.2010.07.20

A common design looks like a high tunnel.Unlike a greenhouse, which uses a heating system, a hoop house is heated by the warmth of the sun.

VOA: special.2009.12.22

The first step uses a bit of influenza DNA to get the patient's immune system to begin fighting off the flu, and then the protection is given a "boost" some time later by the second step, which can be either another bit of DNA or a conventional flu vaccine.

VOA: standard.2010.07.21