1. Chemical analysis of ecological materials;Allen,1974
2. The use of animal wastes for fertilisers;Armstrong;J. Agric. S.A.,1972
3. Higher copper mineral mixture for fattening pigs;Barber;Chem. and Ind.,1955
4. Potentials and limits of organic wastes in crop production;Bassam;Compost Science/Land Utilization,1979
5. The disposal of copper-enriched pig manure slurry on grassland;Batey;J. Br. Grassld Soc.,1972