DIN SPEC 1099
DIN SPEC 1099 Fertilizers - Extraction of phosphorus soluble in 2 % citric acid; German version CEN/TS 15920:2009
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 02/01/2010
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 02/01/2010