1. (4) Müller E. Die Elektrometrische Messanalyse (1928), 2nd ed., p. 78.
2. (5) Prescott J. A. and Piper C. S. Commonwealth of Australia, Council for Scientific and Industrial Research. Pamphlet No. 8, pp. 39–40.
3. (2) Cavanagh B. J.G.S. (1927), p. 2207.
4. (3) Clark W. M. The Determination of Hydrogen Ions (1922), 2nd ed., p. 106.