In the book by  [Bensoussan and Lions](https://www.amazon.co.uk/Impulse-control-quasi-variational-inequalities-Bensoussan/dp/2040155775), they introduce the weighted spaces with exponentially decaying weights to study elliptic equations with bounded coefficients on the whole space $\mathbb{R}^n$. They mentioned that there are classical regularity results based on these spaces.


For example, for each $p\in [1,\infty)$, the weighted $L^p_\mu(\mathbb{R}^d)$ space on $\mathbb{R}^d$ is defined to be the set of Lebesgue measurable functions such that $f\omega_\mu(x)\in L^p(\mathbb{R}^n)$, i.e.,
$$\|f\|_{L^p_\mu}=\int_{\mathbb{R}^d}|f|^p\omega^p_\mu(x)\,dx< \infty,$$ where  $\omega_\mu(x)=\exp(-\mu\sqrt{1+|x|^2})$ for $\mu>0$, and the weighted sobolev space $W^{1,p}_\mu(\mathbb{R}^d)$ is defined to be the space of functions such that $u\omega_\mu\in L^p(\mathbb{R}^n)$ and $\partial_{x_i} u\omega_\mu\in L^p(\mathbb{R}^n)$,
where $\partial_{x_i}$ denotes the weak derivative in the distribution sense. Similarly we define the high-order sobolev space $W^{2,p}_\mu(\mathbb{R}^d)$ such that $\partial_{x_ix_j}u\omega_\mu\in L^p$ for all $i,j$. 


I am interested in a reference on the embedding properties between spaces of different orders. For example, it is pointed out (without a proof) in the book that the injection 
$$
W^{2,p}_\mu\hookrightarrow W^{1,p}_\nu \tag{1}$$
 with $\nu>\mu$ is compact. Could you provide a reference for a proof of this statement? Does it follow from the results for the classical sobolev space?  

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Note that Corollary 3.3 in [Hooton's paper](https://core.ac.uk/download/pdf/82623799.pdf) implies   the injection $W^{2,p}_\mu\hookrightarrow W^{1,p}_\mu \tag{2}$ 
is not compact.