1. Laboratory tests for ascertaining the condition of activated sludge;Ardern,1936
2. Protozoa as indicators in activated-sludge treatment;Baines;Sewage ind. Wastes,1953
3. An illustrated key to the British Freshwater Ciliated Protozoa commonly found in activated sludge;Curds,1969
4. Oekologie der Saprobien;Kolkwitz,1950