Possible Clues:

• “Nightfall” author
• ''The End of Eternity'' author
• Author of 'Three Laws of Robotics'
• Isaac, sci-fi writer
• Isaac —, sci-fi author
• Isaac —, sci-fi author
• Editor of 'The Hugo Winners' anthology series
• Isaac --, American author and scientist 1920-1992
• Isaac --, author of 'I, Robot' (1950)
• ''The Naked Sun'' author Isaac