1. AOACI. Official method 985.01 metals and other elements in plants and pet foods, inductively coupled plasma spectroscopic method . In:Official methods of analysis of AOAC International. 16th ed. Arlington, Va: AOAC International, 1995 ;4 .
2. R Puls .Mineral levels in animal health: diagnostic data. 2nd ed. Aldergrovem, BC, Canada: Sherpa International, 1994 ;6 :313 .