Zecharia Sitchin's main theme in his books is that ancient astronauts visited Earth in the distant past and influenced human civilization. Sitchin claimed that the Sumerians had knowledge of these astronauts, whom they called the Anunnaki, and that he was able to decipher their writings and learn about their history.
The Mythical World of Zecharia Sitchin: Exploring Ancient Astronauts through English Quiz