1. Abraham, Z., Lépine, J.R.D., Braz, M.A.: H66-alpha radio recombination line observations of southern H II regions. Mon. Notices Roy. Astron. Soc. 193, 737 (1980). Determination of electron temperature in H II regions from radio recombination lines. The results mentioned in Section 8.6 are from this reference
2. Aller, L.H.: Physics of Thermal Gaseous Nebulae. Kluwer, Dordrecht (1984). Basic text about physical processes in ionized nebulae, with a discussion on the heating processes, excitation conditions, and abundance determination
3. Bowers, R.L., Deeming, T.: Astrophysics II. Jones and Bartlett, Boston (1984). Referred to in Chapter 1. Includes a good discussion on ionized hydrogen regions
4. Costa, R.D.D., Chiappini, C., Maciel, W.J., Freitas, P.J.A.: New abundances of southern planetary nebulae. Astron. Astrophys. Suppl. 116, 249 (1996). Plasma diagnostics and abundance determination in planetary nebulae in the Galaxy. The results mentioned in Section 8.7 are taken from this reference
5. Dyson, J., Williams, D.A.: The Physics of the Interstellar Medium. Institute of Physics Publishing, London (1997). Referred to in Chapter 1. Includes a quite accessible discussion on ionized H interstellar regions, their temperatures, and dynamical processes