  We give the correct analytic expression of a finite integral appearing in the
four-loop computation of the renormalization-group functions for the
two-dimensional nonlinear sigma-model on the square lattice with standard
action, explaining the origin of a numerical discrepancy. We revise the
numerical expressions of Caracciolo and Pelissetto for the perturbative
corrections of the susceptibility and of the correlation length. For the values
used in Monte Carlo simulations, N=3, 4, 8, the second perturbative correction
coefficient of the correlation length varies by 3%, 4%, 3% respectively. Other
quantities vary similarly.
