" I'm reading Asimov according to his own published reading list. It's quite a jump between Robots & Empire and this according to the story chronology, and also a big jump back in time according to publication date chronology. It's interesting how one somewhat unexplained fact, like Earth being radioactive, could be woven so tightly into a story written after, but set earlier than this one. This has been something I've noted about many sci-fi series before. If I ever write anything, I'll be sire to include some big plot element that is never explained, so that I may write stories chronologically earlier that give depth to chronologically later stories already written. "
— Cory, 2/18/2014