1. Council directive of 21 May concerning urban waste water treatment,1991
2. European Water Pollution Control Association (EWPCA), The Comparability of Quantitative Data on Waste Water Collection and Treatment, Final report to the EC DG XI B1, CEC Study Contract no. B4/3040/93/000924/JS/B1.
3. Instrumentation, control and automation of water and wastewater treatment and transport systems;Water Sci. Tech.,1997