1840. Black sheep in the copper family: Wiener, G., Field, A. C. & Wood, Jean (1969). The concentration of minerals in the blood of genetically diverse groups of sheep. I. Copper concentration of different seasons in Blackface, Cheviot, Welsh Mountain and crossbred sheep at pasture. J. agric. Sci., Camb.72, 93. Wiener, G. & Field, A. C. (1969). Copper concentrations in the liver and blood of sheep of different breeds in relation to swayback history. J. comp. Path. Ther.79, 7