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aChicago South District Filtration Plant, Department of Water and Sewers, Chicago, Illinois
2
Water Bacteriologist IV.
3
Chief Water Chemical Engineer, Chicago South District Filtration Plant, Department of Water and Sewers, Chicago 49, Illinois.
1
A research project carried on in cooperation with L. R. Hedrick, Chairman, and Marjorie L. Sutherland, Biostatistician, Biology Department, Illinois Institute of Technology, Chicago 16, Illinois.