  We establish an integration by parts formula in bounded domains for the
higher order fractional Laplacian $(-\Delta)^s$ with $s>1$. We also obtain the
Pohozaev identity for this operator. Both identities involve local boundary
terms, and they extend the identities obtained by the authors in the case
$s\in(0,1)$.
  As an immediate consequence of these results, we obtain a unique continuation
property for the eigenfunctions $(-\Delta)^s\phi=\lambda\phi$ in $\Omega$,
$\phi\equiv0$ in $\mathbb R^n\setminus\Omega$.

Analysis of PDEs