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Topical Subjects
- Coal Mines and Mining--Laboratories.22
- Coal Mines and Mining--Machinery.2
- Coal Mines and Mining--Miners at Work.1
- Coal mines and mining--Equipment and supplies.2
- Coal mines and mining--West Virginia--Thomas.1
- Coal--Testing.21
- Coal-mining machinery.1
- Electric current rectifiers.2
- Factories--West Virginia1
- Industrial equipment.[remove]26
- Rectifier instruments.2
- Research, Industrial--Laboratories.23