  Using the celebrated Witten-Kontsevich theorem, we prove a recursive formula
of the $n$-point functions for intersection numbers on moduli spaces of curves.
It has been used to prove the Faber intersection number conjecture and
motivated us to find some conjectural vanishing identities for Gromov-Witten
invariants. The latter has been proved recently by X. Liu and R. Pandharipande.
We also give a combinatorial interpretation of $n$-point functions in terms of
summation over binary trees.
