In Theorem 5.2 of the book
Robert A. Adams and John J. F. Fournier, MR 2424078 Sobolev spaces, ISBN: 0-12-044143-8.
is stated that, for any integers $0 \leq j \leq m$ and $u \in W^{m,p}(\Omega)$ (under suitable assumptions on $\Omega$), the following interpolation inequality holds $$ \|u\|_{W^{j,p}} \lesssim \|u\|^{j/m}_{W^{m,p}} \cdot \|u\|_{L^p}^{(m-j)/m}. $$
Is there an analogous result for Sobolev spaces of fractional order? (I am particularly interested in the case $p=2$).