Ciro riconosciuto by Leonardo Leo

[RobertoBln65]

Dear all,
I have noticed that the scores of Leonardo Leo’s Ciro riconosciuto have
been distinguished in two versions, 1739 and 1742. In addition, the singers
of both versions have been listed. Can somebody explain me, how she/he
could assign the three scores to both versions and how she/he could find
the singers of the version 1742? As far I know, there is no libretto of the
1742 version. Did you find a source?
Thank you in advance,
Roberto