H-ZF71 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.406805\,\lambda^2}{\lambda^2 - 0.0645152} + \frac{1.70831\,\lambda^2}{\lambda^2 - 0.0127703} + \frac{2.36137\,\lambda^2}{\lambda^2 - 163.276}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-9.66 \times 10^{-6} + 2(1.15 \times 10^{-8})\,\Delta T + 3(-5.06 \times 10^{-11})\,\Delta T^2 + \frac{9.75 \times 10^{-7} + 2(1.26 \times 10^{-9})\,\Delta T}{\lambda - 0.313}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$