to estimate solely from optical conductivity measurements. One can expect such correlations to redistribute the Drude spectral weight giving an effective mass of the quasiparticles, $m^*$, different from the band mass, $m_b$. Such mass renormalizations can be extracted using extended Drude model analysis but as argued before, it would be unreliable in the present context because of the low lying inter-band transitions. However we can roughly characterize the renormalization effect by spectral weight analysis. We make use of the conductivity sum rule $$\dfrac{Z_0}{\pi^2}\int_0^{\omega_c} \sigma_1(\omega) d\omega = \omega_p^2 = \dfrac{4\pi n e^2}{m_b}$$ where $Z_0$ is vacuum impedance, $n$ is the carrier density and $\omega_c$ is chosen appropriately to include the bandwidth of interest. If we interpret both the Drude term and peak at 200 cm$^{-1}$ both as inter-band contributions, then the ratio of the total spectral weight to the Drude piece gives a measure of the renormalized mass. A naive estimate of this electron-magnon coupling constant from this exercise, $\gamma = m^*/m_b -1 = 0.4$. This is however a rather crude estimate as we know that there is a finite contribution to the conductivity at these frequencies from inter-band transitions and hence these numbers are only a rough guide. It would 