Subject
- Crawler tractors -- Oregon2
- Douglas fir -- Harvesting -- Oregon2
- Forest thinning -- Oregon2
- Crawler tractors1
- Crawler tractors -- Customizing1
- Farm tractors -- Economic aspects -- Oregon -- Marion County1
- Logging -- Machinery1
- Tractor trailer combinations -- Cost of operation1
- Tractor trailer combinations -- Evaluation1
- Tractor trailer combinations -- Oregon1