  Cohen, Guyon, Perrin and Pontier have given assumptions under which the
second-order quadratic variations of a Gaussian process converge almost surely
to a deterministic limit. In this paper we present two new convergence results
about these variations: the first is a deterministic asymptotic expansion; the
second is a central limit theorem. Next we apply these results to identify
two-parameter fractional Brownian motion and anisotropic fractional Brownian
motion.
