Subject
- Metals--Extrusion4
- Michigan--Tittabawassee River4
- Microscopes4
- Refuse and refuse disposal4
- Scientific apparatus and instruments--Calibration4
- Tabulating machines4
- Women chemists4
- Colombia--Cartagena3
- Conveying machinery3
- Greenhouses3
- Machine parts3
- Machine parts--Maintenance and repair3
- Machine parts--Standards3
- Microscopy3
- Presidents3
- Research, Industrial--Laboratories3
- Scientists, Black3
- Soil fumigation3
- African American chemists2
- African American women2