The loop entropy formula becomes more complicated with multiples loops, but may be determined for a Gaussian polymer using a matrix method developed by Wang and Uhlenbeck. Let there be M contacts among the residues, which define M loops of the polymers. The Wang-Uhlenbeck matrix W is an M × × M symmetric, real matrix whose elements W i j equal the number of common residues between loops i and j . The entropy of making the specified contacts equals