H-ZF88 by CDGM

$$n(\lambda) = \sqrt{1 + \frac{2.04275\,\lambda^2}{\lambda^2 - 0.0169743} + \frac{1.98276\,\lambda^2}{\lambda^2 - 109.068} + \frac{0.504268\,\lambda^2}{\lambda^2 - 0.0751711}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-3.58 \times 10^{-6} + 2(1.75 \times 10^{-8})\,\Delta T + 3(-4.67 \times 10^{-11})\,\Delta T^2 + \frac{1.18 \times 10^{-6} + 2(1.91 \times 10^{-9})\,\Delta T}{\lambda - 0.33}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$