1. Crop evapotranspiration – guidelines for computing crop water requirements;Allen;FAO Irrig. Drain. Paper,1998
2. Dilution of non-point source nitrate in groundwater;Altman;J. Environ. Qual.,1995
3. Aquakem 600A (Konelab 60), 2006. Aquakem Reference Manual. Thermo Electron OY, Clinical Diagnostics, Clinical Chemistry and Automation Systems, Ratasie 2, Vantaa, Finland.
4. Askew, F.E., Smith, R.K., 2005a. Inorganic non-metallic constituents, 4500-SO42-; Sulfate; Method 4500-SO42- E. Turbimetric method. In: Eaton, D.A., Clesceri, L.S., Rice, E.W., Greensberg, A.E. (Eds.), Standard Methods for the Examination of Waters and Waste Water, 21st ed. American Public Health Association, NW Washington, DC, pp. 4–188. ISBN 0-87553-047-8 (2001-3710).
5. Askew, E.F., Smith, R.K., 2005b. Part 4000, Inorganic and non-metallic constituents. Persulfate method for simultaneous determination of total nitrogen and total phosphate. 4500-P J. In: Eaton, A.D., Clesceri, L.S., Rice, W.E., Greenberg, A.E. (Eds.), Standard Methods for the Examination of Water and Wastewater, 21st ed. American Public Health Association, Washington, DC, pp. 4.160–4.162. ISBN 0-87553-047-8.