1. Cohen ER, Cvitas T, Frey JG, Holmström B, Kuchitsu K, Marquardt R, Mills I, Pavese F, Quack M, Stohner J, Strauss HL, Takami M, Thor AJ (2008) Quantities, units and symbols in physical chemistry, IUPAC Green Book, 3rd edn. IUPAC & RSC Publishing, Cambridge, p 74, 2nd printing
2. Cox JD (1982) Pure Appl Chem 54:1239
3. Wanner H, Önsted E (2000) Standards and conventions for TDB Publications. OECD Nuclear Energy Agency, p 3
4. Nernst W (1900) Z Elektrochem7:253
5. Galster H (1991) pH measurement: fundamentals, methods, applications, instrumentation. Weinheim, VCH, p 68