1. Combined effects of cadmium and nickel on the activated sludge process;Bagby;J. Water Pollut. Control Fed.,1981
2. Removing soluble metals from wastewater;Metzner;Water Sewage Works,1977
3. Anaerobic waste treatment fundamentals;McCarty;Public Works,1964
4. Metals in Activated Sludge Removal and Effects;Nielsen,1981