Andrei Okounkov, Rahul Pandharipande. Gromov–Witten Theory, Hurwitz Theory, and Completed Cycles. Annals of Mathematics. 2006.
Andrei Okounkov, Rahul Pandharipande. Gromov–Witten Theory, Hurwitz Theory, and Completed Cycles. Annals of Mathematics. 2006.