He spent the next two years researching the story.

She spent four years researching wolves while working on the novel.

He spent over 30 years researching the battle and its participants.

David has spent the last nine years researching the Great Wall.

Hoh has spent more than 40 years researching the history of the circus.

He spent almost 20 years researching the life of Khrushchev in preparation to write his book.

After finding no suitable explanation he spent the next fifty years researching the answer.

He has twenty years experience researching the golf industry worldwide.

He spent three years researching the book, which has detailed listings for 200,000 seasonal jobs.

It was the main reason they had spent years researching for good men.