1. Commission of the European Communities, Council Regulation (EEC) No. 1576/89, Off. J. Eur. Commun. L 160 (1989) 0001.
2. DOG 193, Orde de 16 de setembro de 1993, Diario Oficial de Galicia 193 (1993) 6640.
3. BOE 194, Orden APA/2668/2005 de 20 de Julio de 2005, Boletín Oficial del Estado 194 (2005) 28516.
4. Preconcentration of trace elements in potable liquids by means of a liquid membrane emulsion for flame atomic absorption determination
5. Statistical Procedures in Food Research;Piggott,1987