# Chern numbers of almost complex manifolds

Suppose we are given two integer numbers $p$ and $q$ such that $p+q\equiv 0 \pmod{12}$. There is a result saying that for every such pair there exists a non necessarily connected almost complex manifold of dimension $4$ such that its Chern numbers are equal to $p$ and $q$. Could you give me a reference for the proof of this result?