Simplify the following text for a Grade 12 native English-speaking person.
Original: The Three Laws form an organizing principle and unifying theme for Asimov 's fiction , appearing in his Robot series and the other stories linked to it , as well as his Lucky Starr series of science-oriented young-adult fiction .
Simplified: The Three Laws form an organizing principle and unifying theme for Asimov 's fiction , appearing in his Robot series , the other stories linked to it and his Lucky Starr series of young-adult fiction .