Let $B$ be an $\ell_2$-ball of radius $r$ in $\mathbb{R}^n$.
I want to find the cardinal of a (not too big) $\epsilon$-net of $B$, that is the cardinal of a finite set $V\subset B$ such that $\forall x\in B,\exists y\in V, \|x-y\|_2\leq \epsilon$. I guess there exists an $\epsilon$-net of cardinal $\mathcal{O}\left(\frac{r^n}{\epsilon^n}\right)$ but I miss the constant. Are there precise references on the topic ?