Combee, Jerry H.  "Nietzsche as Cosmologist: The Idea of the Eternal Recurrence as a Cosmological Doctrine and Some Aspects of Its Relation to the Doctrine of the Will to Power."  Interpretation 4, no. 1 (Winter 1974): 38-47.

Excerpt:

“In the last speech of part 2 of Thus Spoke Zarathustra,1 Zarathustra

teUs his friends that there is stUl something more he could teU them.
Evidently Zarathustra’s final teaching has not been revealed; perhaps
it is that teaching is incomplete by itself. In Ecce Homo, Nietzsche reports
that when he “found Zarathustra III” he was
“finished,”
and he also
says that “the fundamental conception of this work
(Zarathustra)” is
“the idea of the eternal recurrence.”2The first speech of part 3 of Thus
Spoke Zarathustra contains what appears to be a dramatic re-creation on
a much grander scale of the occasion of Nietzsche’s finding of the idea
of the eternal recurrence as described in Ecce Homo;3 in the second
speech of part 3, Zarathustra first reveals his teaching on the eternal
recurrence, though not to his friends.4 Relying on this passage in
Zarathustra and certain others in other works,5 the essence of the idea
of the eternal recurrence may be distilled into the following proposition:
aU things that can occur have occurred and wiU recur in the same
succession an infinite number of times.6”

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