# Finite Difference Methods for arbitrary elliptic PDE

I am looking for textbook references that describe lattice numerical methods for arbitrary elliptic PDEs, particularly finite difference schemes and particularly in 2d. The few references that I have looked at only treat the laplacian or the heat equation, I would like the more general case when the differential operator does not have constant coefficients, ie $$Lu = A(x,y) u_{xx} + B(x,y) u_{xy} + C(x,y) u_{yy}.$$