}, A., E., G., {., E., A.(1981).Standard Methods for the Examination of Water and Wastewater 18th Edition 1992 (fifteenth edition).Washington DC:American Public Health Asociation.
Gaya MLA
}, A., E., G., {., E., A..Standard Methods for the Examination of Water and Wastewater 18th Edition 1992.fifteenth editionWashington DC:American Public Health Asociation,1981.Text.