FYI:

Erich von Däniken is Swiss not Dutch. He isn't exactly what I'd call a fraud as he didn't make things up but interpreted evidence in a - well - biased fashion. But to speak on his behalf: he did make several expeditions to investigate his own claims and withdrew some of the wildest ones later.
In my youth his books were fun to read because I was already infected by the spacefaring virus and I didn't care whether the rockets came from Alabama, Kapustin Jar or Alpha Centauri.

Extracelestial

__________________
Science is not a monument of received Truth but something that people do to look for truth. - Dennis Overbye