The researchers used an electron microscope and fossilized remains of thirty feathers that once covered the animal.

VOA: special.2010.03.16

Once growth is established, the box can be removed and used to start another planting.

VOA: special.2010.07.13

The meetings used to be held about once every two years.

VOA: special.2009.06.03

She says the online tool was very effective for those who used it at least once a month.

VOA: standard.2010.07.30

"I think you get used to it after a while." "Once in a while it will get worse, so then it is a little bit nauseating, but it is actually fine, it is not too bad,I am used to it."

VOA: standard.2010.07.30