"Liar" and "Reason" were written and published first, but "Runaround" was
the story in which the Three Laws were appeared in its entirety! In fact,
that same issue of ASTOUNDING in which "Runaround" appeared had a seperate
page where the laws were listed.
The Zeroeth Law was first appeared in ROBOTS OF DAWN where Giskard was
explaining his actions to Bailey at the end of the novel. However I could
be wrong in this last part 'cause it's been a while since I read it. It
might have just been inferred in DAWN and completely explained in ROBOTS AND
EMPIRE.
.sig file under construction!!!