Is there a special name for an integral of the form $$\int d \vec{r} \int d \vec{r}\,'\, f(\vec{r})\, K(\vec{r} - \vec{r}\,')\, f(\vec{r}\,')\; ?$$ Here $\vec{r}, \vec{r}\,' \in R^d$, and the integrals are over all $R^d$.
In my case, $f$ and $K$ are real, but not necessarily positive, functions. Furthermore, $K$ is even in its argument.
Are there any particular results on integrals of this form? One can use the convolution theorem to express this integral in various ways depending on the Fourier transforms of $f$ and $K$, for instance. Are there any others which may be of use in finding closed-form expressions?