著者
Iowa State University. Cooperative Extension Service
3
Iowa Agriculture and Home Economics Experiment Station
2
Iowa Farm Bureau
2
Iowa Farm Bureau Federation
2
Iowa State College. Agricultural and Home Economics Experiment Station
2
Iowa Agricultural Experiment Station
1
Iowa Farm Business Association
1
Iowa State College. Extension Service
1
Iowa State College. Extension Service. Agricultural Economics Section
1
Iowa State University. Agricultural and Home Economics Experiment Station
1
United States. Department of Agriculture
1