  The paper studies a bounded symmetric operator ${\mathbf{A}}_\varepsilon$ in
$L_2(\mathbf{R}^d)$ with $$ ({\mathbf{A}}_\varepsilon u) (x) =
\varepsilon^{-d-2} \int_{\mathbf{R}^d} a((x-y)/\varepsilon) \mu(x/\varepsilon,
y/\varepsilon) \left( u(x) - u(y) \right)\,dy; $$ here $\varepsilon$ is a small
positive parameter. It is assumed that $a(x)$ is a non-negative
$L_1(\mathbf{R}^d)$ function such that $a(-x)=a(x)$ and the moments $M_k
=\int_{\mathbf{R}^d} |x|^k a(x)\,dx$, $k=1,2,3$, are finite. It is also assumed
that $\mu(x,y)$ is $\mathbf{Z}^d$-periodic both in $x$ and $y$ function such
that $\mu(x,y) = \mu(y,x)$ and $0< \mu_- \leq \mu(x,y) \leq \mu_+< \infty$. Our
goal is to study the limit behaviour of the resolvent
$({\mathbf{A}}_\varepsilon + I)^{-1}$, as $\varepsilon\to0$. We show that, as
$\varepsilon \to 0$, the operator $({\mathbf{A}}_\varepsilon + I)^{-1}$
converges in the operator norm in $L_2(\mathbf{R}^d)$ to the resolvent
$({\mathbf{A}}^0 + I)^{-1}$ of the effective operator ${\mathbf{A}}^0$ being a
second order elliptic differential operator with constant coefficients of the
form ${\mathbf{A}}^0= - \operatorname{div} g^0 \nabla$. We then obtain sharp in
order estimates of the rate of convergence.
