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Subject
- Corporations5
- Water5
- Water--Purification5
- Scientific apparatus and instruments4
- Insecticides3
- Perkin-Elmer Corporation3
- United States. Environmental Protection Agency3
- Water quality3
- Water quality--Testing3
- Water--Purification--Coagulation3
- Water--Purification--Filtration3
- Water--Softening3
- Advertising2
- Advertising, Industrial2
- Beckman Instruments, Inc.2
- Chemical industry2
- DDT (Insecticide)2
- Employees2
- Insect pests--Control2
- Laboratories2