H-ZPK1A by CDGM

$$n(\lambda) = \sqrt{1 + \frac{0.944049\,\lambda^2}{\lambda^2 - 109.036} + \frac{1.05017\,\lambda^2}{\lambda^2 - 0.0132904} + \frac{0.527569\,\lambda^2}{\lambda^2 - 0.000741463}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-1.09 \times 10^{-5} + 2(1.14 \times 10^{-8})\,\Delta T + 3(-4.44 \times 10^{-11})\,\Delta T^2 + \frac{4.52 \times 10^{-7} + 2(3.49 \times 10^{-10})\,\Delta T}{\lambda - 0.159}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$