[EM] question: who gets credit for the minimal dominant set?

[James Green-Armytage]

Dear folks,
	If anyone has the answer to this, please let me know. I'm just wondering
who was the first one to come up (and publish) the idea of the minimal
dominant set, as it applies to pairwise comparisons a la Condorcet's
method. 
	As I understand it, the minimal dominant set is the smallest set such
that all candidates inside the set pairwise-beat all candidates outside
the set.
	I know that Schwartz defined it in 1986, but I'm guessing that it was
defined some time before that... but if so, I don't know when, or by whom.
Can anyone help me here?

my best,
James