The number of non-homogeneous lattice points in plane subsets
Michael Mather · Mathematical Proceedings of the Cambridge Philosophical Society · 1978
Let Z2 denote the integer lattice in the plane, let A be a non-singular 2 x 2 matrix and let c ∈ R2. Then G = AZ2 + c is called a grid, and its determinant det G is defined to be det A. The grid G is called a subgrid if G ⊂ Z2.