But she says the research does show the need to study whether or not there are long-lasting effects of repeated exposure over several years.

VOA: special.2011.03.02

Under the agreement, painstakingly negotiated with the outgoing Japanese government over several years, the United States will move 8,000 U.S.Marines from the Futenma base on Japan's southern island of Okinawa to the U.S.

VOA: standard.2009.08.31

Over the years,researchers have identified several substances in the blood that can serve as what they call cardiac biomarkers.

VOA: special.2009.07.15

She says her students over the past several years have increasingly used less formal English in their writing.

VOA: special.2010.01.28

Defects have been linked to at least thirty-nine deaths over the past several years.

VOA: special.2010.02.26

Over the years, several attempts were made to build the canal.

VOA: special.2010.08.12

Over the next several years, many Americans lost their jobs.

VOA: special.2010.06.13

Over the next several years he bought more theaters.

VOA: special.2009.05.31

South Korean farmers have held occasionally violent demonstrations over the years, and several farmers have committed suicide to protest the agreement.

VOA: standard.2009.04.22

"Over the past several years, I have had the honor to call Teddy a colleague, a counselor and a friend,"

VOA: standard.2009.08.26

Johnson says that her students, over the past several years, have increasingly used a more informal English vocabulary in formal assignments.

VOA: standard.2010.01.16

You can expect to see a lot more from us in terms of investigations of individuals and institutions over the next several years."

VOA: standard.2009.08.19

Republicans and many conservative Democrats are balking on the cost of the reform, which could reach one trillion dollars over the next several years.

VOA: standard.2009.09.04

"If you look at the large studies, that were published over the last several years, including a large number of patients comparing Avandia to a placebo or other drugs, there was actually no increase in that risk.

VOA: standard.2010.03.02

"We know that surface use of dispersants decreases the environmental risk to shorelines and organisms at the surface and we know that dispersants break down over weeks rather than remaining for several years as untreated oil might."

VOA: standard.2010.05.18