On multiply monotone functions

In this paper, the algebra of the differences of two multiply monotone functions on $\mathbb{R}_+=(0,+\infty)$ is studied. A sufficient condition for the function $f_0\big(|x|_{p,d}\big)$, where $|x|_{p,d}=\Big(\sum\limits_{j=1}^d|x_j|^p\Big)^{\frac{1}{p}}$, $p\in(0,+\infty]$, to be represented as the Fourier transform is given.