Milk - Determination of nitrogen content - Part 4: Determination of the non-protein-nitrogen content (ISO 8968-4:2001); German version EN ISO 8968-4:2001— 11 стр.
Milk and milk products - Determination of nitrogen content - Part 1: Kjeldahl principle and crude protein calculation (ISO 8968-1:2014); German version EN ISO 8968-1:2014— 26 стр.
Milk and milk products - Determination of nitrogen content - Part 4: Determination of protein and non-protein nitrogen content and true protein content calculation (Reference method) (ISO 8968-4:2016); German version EN ISO 8968-4:2016— 21 стр.