$$\bex n\geq 2, 1\leq p<n\ra \sen{f}_{L^\frac{np}{n-p}(\bbR^n)} \leq C\prod_{k=1}^n \sen{\p_k f}_{L^p(\bbR^n)}^\frac{1}{n}. \eex$$
$$\bex n\geq 2, 1\leq p<n\ra \sen{f}_{L^\frac{np}{n-p}(\bbR^n)} \leq C\prod_{k=1}^n \sen{\p_k f}_{L^p(\bbR^n)}^\frac{1}{n}. \eex$$