http://www.legislation.gov.uk/nisr/1991/540/schedule/2/crossheading/determination-of-the-fineness-of-grinding-of-soft-natural-phosphates/paragraph/2/madeThe Fertilisers (Sampling and Analysis) Regulations (Northern Ireland) 1991Local GovernmentGovernment Printer for Northern Ireland2016-09-06AGRICULTURESCHEDULE 2METHODS OF ANALYSIS15b.DETERMINATION OF THE FINENESS OF GRINDING OF SOFT NATURAL PHOSPHATESFIELD OF APPLICATION2Soft natural phosphates.