The Direct Solution of the Discrete Poisson Equation on Irregular Regions
B.L. Buzbee, F. W. Dorr, J. A. George, G. H. Golub · SIAM Journal on Numerical Analysis · 1971
There are several very fast direct methods which can be used to solve the discrete Poisson equation on rectangular domains. We show that these methods can also be used to treat problems on irregular regions.