Giorgi, J. (2009). Math for wastewater treatment operators grades 1 and 2: A guide to preparing for wastewater treatment operator certification exams. American Water Works Association.
Lua i Stíl Chicago (17ú heag.)Giorgi, John. Math for Wastewater Treatment Operators Grades 1 and 2: A Guide to Preparing for Wastewater Treatment Operator Certification Exams. Denver, Colo.: American Water Works Association, 2009.
Lua MLA (9ú heag.)Giorgi, John. Math for Wastewater Treatment Operators Grades 1 and 2: A Guide to Preparing for Wastewater Treatment Operator Certification Exams. American Water Works Association, 2009.
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