1. Box, G. E. P., Hunter, W. G., and Hunter, J. S. Statistics for Experimenters, p. 320. John Wiley and Sons, Inc.: New York, 1978.
2. European Brewery Convention. Analytica-EBC (3rd ed.). Methods 6.3.1, p. E47; 6.3.2, p. E49; 6.3.3, p. E52; Schweizer Brauerei-Rundschau: Zurich, 1975.
3. EUROPEAN BREWERY CONVENTION ANALYSIS COMMITTEE SUB-COMMITTEE ON ANALYSIS OF HOPS AND EXTRACTS: METHODS OF ANALYSIS OF HOP-EXTRACTS