1. Swiss Parliament, Sewage Sludge Decree of April 8, 1981.
2. Federal Republic of Germany, Sewage Sludge Decree of June 25, 1982.
3. Environmental regulations and technology: use and disposal of municipal wastewater sludge;United States Environmental Protection Agency;EPA 625/10-84-003,1984
4. Pathogens in sludge: occurrence, inactivation, and potential for regrowth;Ward,1984