F. WITTWER, P. CONTRERAS, N. SILVA, and H. BÖHMWALD, “Effects of magnesium supplementation as magnesium oxide in food or magnesium sulphate in water on the prevention of hypomagnesaemic tetany and blood and urine magnesium concentrations in hypomagnesaemic Hereford herds”, Arch med vet, vol. 29, no. 1, pp. 25–33, Jun. 1997.