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We prove that there is a universal constant $c\\in\\mathbb{N}$ such that, if $F$ is the unit ball of a separable reproducing kernel Hilbert space, then \\[ g_{cn}(F)^2 \\,\\le\\, \\frac{1}{n}\\sum_{k\\geq n} d_k(F)^2, \\] where $d_k(F)$ are the Kolmogorov widths (or approximation numbers) of $F$ in $L_2$. 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We prove that there is a universal constant $c\\in\\mathbb{N}$ such that, if $F$ is the unit ball of a separable reproducing kernel Hilbert space, then \\[ g_{cn}(F)^2 \\,\\le\\, \\frac{1}{n}\\sum_{k\\geq n} d_k(F)^2, \\] where $d_k(F)$ are the Kolmogorov widths (or approximation numbers) of $F$ in $L_2$. 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