\begin{equation*}   \ T_{0,2}=\sqrt{\frac{m_0}{m_2}}=\sqrt{\frac{\int_{f=0}^{+\infty}\int_{\theta=0}^{2\pi} S(f,\theta)df.d\theta}{\int_{0}^{2\pi}\int_{f=0}^{+\infty} f^2S(f,\theta)df.d\theta}}   \end{equation*}
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