State University. Extension Service, Oregon, Washington State University. Extension, United States. Dept. of Agriculture, University of Idaho. Extension, Robert L Stebbins, and Pacific Northwest Cooperative Extension. 1992. Training Pear Trees In Commercial Orchards. : [Corvallis, Or.] : Oregon State University, Extension Service ; [Pullman, Wash.] : Washington State University Extension ; [Moscow, Idaho] : University of Idaho Extension ; [Washington, D.C.] : U.S. Dept. of Agriculture.