He also wrote books on art for young people, some in collaboration with his wife.

These works were done in collaboration with his brother, Paul.

Many of his books were written in collaboration with others.

Much of his later work was also written in collaboration with others.

Several more books followed, some written in collaboration with others.

He found it very difficult to work in collaboration with others.

The production is designed in close collaboration with the industry.

"Art and science used to be in collaboration up until early this century," he said.

They are often in collaboration with community leaders and partners.

It would be very interesting to look into this further perhaps in collaboration with you.