Complex sentence: "Black Destroyer" is a science fiction short story by A. E. van Vogt which was first published in the magazine "Astounding" in July 1939--the start of the Golden Age of Science Fiction.
Split into simpler sentences: Black Destroyer is a science fiction short story by A. E. van Vogt which was first published "Astounding" in July 1939. It has been marked as the story that represents the start of the Golden Age of Science Fiction.