1. Addinsoft (1995–2002) XLStat-pro. 5.1 Version 4, Paris, France
2. Antweiler RC, Goolsby DA, Taylor HE (1995) Nutrients in the Mississippi River. US Geological Survey Circular 1133. USGS, Denver
3. APHA (1975) Standard methods for the examination of water and waste water, 14th edn. American Public Health Association, Washington DC
4. APHA (1995) Standard methods for the examination of water and wastewater, 19th edn. American Public Health Association/American Water Works Association/Water Environment Federation, Washington DC
5. Back W (1961) Techniques for mapping of hydrochemical facies. USGS Prof. Pap., vol 424D, pp 380–382