4) Y. Terashima and M. Ishikawa:“Kinetic Analysis of BOD and Nitrogen Removal in an Oxidation Ditch”, Wat. Sci. Tech., 17 (Amsterdam), 291 (1984).
5) G. A. Ekama and G. v. R. Marais:“Nitrification” in Theory, design and operation of nutrient removal activated sludge processes, Water Research Commission, Pretoria (1984). Chapter 5.