The period at the turn of the 1880s and 1890s was associated with intensive work on several novels.

Two hours and twenty years of intensive work would be concluded.

Since April 1956 there has been intensive work to clear the pollution.

They require intensive work over a long period of time.

This includes three to five weeks of intensive work with their new owner.

Particularly intensive work on them began early in May 1939.

That is the result of intensive work lasting over three years.

This has involved intensive regulatory work over the last year.

We have behind us a long period of very intensive cooperative work.

Americans increasingly stay for months or years of intensive work rather than a few days.