Some remarks on the duality method for Integro-Differential equations with measure data

We deal with existence, uniqueness, and regularity for solutions of the boundary value problem $$\begin{cases} {\mathcal L}^s u = \mu &\quad \text{in $\Omega$}, u(x)=0 \quad &\text{on} \ \ \mathbb{R}^N\backslash\Omega, \end{cases}$$ where $\Omega$ is a bounded domain of $\mathbb{R}^N$, $\mu$ is a bounded radon measure on $\Omega$, and ${\mathcal L}^s$ is a nonlocal operator of fractional order $s$ whose kernel $K$ is comparable with the one of the factional laplacian.