There have been a number of studies looking at the lake's environment and water quality.

He published a number of academic studies during this period.

If the number of studies is very large, then more than 3 groups may be used.

A number of other polls and studies have been done in recent years with various results.

Since then there have been a number of other studies.

Overall, however, evidence is still based on a relatively small number of studies.

A number of studies seemed to show that it was effective.

There are a number of studies now which begin to suggest further cause for concern.

A number of studies have been mounted starting in 1981.