  We study the integro-differential operators $L$ with kernels $K(y) = a(y)
J(y)$, where $J(y)dy$ is a L\'evy measure on $\bR^d$ (i.e.
$\int_{\bR^d}(1\wedge |y|^2)J(y)dy<\infty$) and $a(y)$ is an only measurable
function with positive lower and upper bounds. Under few additional conditions
on $J(y)$, we prove the unique solvability of the equation $Lu-\lambda u=f$ in
$L_p$-spaces and present some $L_p$-estimates of the solutions.
