Cell size of rotated overlapped honeycomb lattices (moire pattern)

Question

Assuming there are two infinity large honeycomb lattices, whose side lengths of their smallest hexagons are a and b, respectively. When one lattice rotates θ relatively to another lattice, a Moire pattern appears which has different repeating unit cells with side length m. What is relation between m, a, b and θ? In wiki(Moire pattern), a solution is given when a=b.