1. Yntema, L. (1909), On the brightness of the sky and total amount of starlight, Publ. Astr. Groningen No 22, 1–55. There are observations on record as early as 1788 of nights with an unusually large sky brightness and an increase in brightness from the zenith to the horizon. That the light of the night sky has a terrestrial component—what is now termed airglow—was suspected by a number of astronomers around 1900 and was definitely established through careful photometry by, Section 6.1 Airglow Photometry
2. “Recherches sur le Spectre Solaire,”;Ångström,1868
3. On the general auroral illumination of the sky and the wavelength of the chief aurora line;Slipher;Astrophys. J.,1919
4. Absolute intensity of the aurora line in the night sky and the number of atomic transitions;Rayleigh;Proc. Roy. Soc. (London),1930
5. A photometric unit for the airglow and aurora;Hunten;J. Atm. Terr. Phys.,1956