  We propose a new fast numerical renormalization group method,the corner
transfer matrix renormalization group (CTMRG) method, which is based on a
unified scheme of Baxter's corner transfer matrix method and White's density
matrix renormalization groupmethod. The key point is that a product of four
corner transfer matrices gives the densitymatrix. We formulate the CTMRG method
as a renormalization of 2D classical models.
