1. American Public Health Association. Standard Methods for the Examination of Water and Wastewater, 14th ed. The Association: Washington, DC, 1976. p. 496.
2. American Society of Brewing Chemists. Report of Subcommittee on Color of Wort:Am. Soc. Brew. Chem., Proc. 1958, p. 160;Proc. 1959, p. 198.