A robot may not injure a human being or, through inaction, allow a human being to come to harm.
A robot must obey any orders given to it by human beings, except where such orders would conflict with the First Law.
A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.
A robot may not harm humanity, or, by inaction, allow humanity to come to harm.
Lyuben Dilov's Forth law:
A robot must establish its identity as a robot in all cases.
Harry Harrison's Forth law:
A robot must reproduce. As long as such reproduction does not interfere with the First or Second or Third Law.
Nikola Kesarovski's Fifth law:
A robot must know it is a robot.