Stebbins, Robert L., Oregon State University. Extension Service, Washington State University. Cooperative Extension, University of Idaho. Cooperative Extension Service, and United States. Department of Agriculture. 1989. Choosing Pear Rootstocks for the Pacific Northwest [1989]. : [Corvallis, Or.] : Oregon State University Extension Service ; [Olympia, Wash.] : Washington State University, Cooperative Extension ; [Moscow, Idaho] : University of Idaho Cooperative Extension Service ; [Washington, D.C.] : U.S. Dept. of Agriculture.