The study was started in 1946 and carried out over the next 20 years.

The last study on this subject was carried out in 1994.

Several studies have been carried out in Germany since the 1970s.

The independent study is being carried out in two parts.

However, the study by the Commission will not be carried out until 2013.

Experts in these nations carry out studies and share information.

It is no good carrying out studies which we are not going to follow up.

Few if any controlled studies have been carried out to answer the question.

Even if such studies were carried out, the answers could not be learned for many years.

The study was carried out in June 1997, and it considered 20 sites.