German standard methods for examination of water, waste water and sludge; physical and physico-chemical characteristics (group C); determination of pH value (C5)— 7 стр.
Accuracy (trueness and precision) of measurement methods and results - Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method (ISO 5725-2:1994 including Technical Corrigendum 1:2002)— 97 стр.