1. McKee, J. E. and Wolf, H. F. 1971.Water Quality Criteria, The Resources Agency of California192 State Water Resources Control Board, Publication 3 - A
2. 1953. Anon, Effluent Standards Proposed to be Adopted by Mersey River Board (England), A discussion.Journal of Sewage and Purification, 4
3. Horwitz, W. 1970. Washington: Official Methods of Analysis of the Association of Official Analytical Chemists. 11th Edition