It is a wonderful thing: your preferred bookstore should have this books so you can buy them. If they don't have at the moment, request them to have soon. They can contact Amazon in the meantime.
One of them, written in English, presents the viewpoints of 23 top UFO investigators at international level, answering the same set of questions. It is so far the only survey developed among experts on the subject.
We are talking about "ALIENS, SHIPS AND HOAXES".