Willett, Mike, and Peter H Westigard. 1988. Using Horticultural Spray Oils to Control Orchard Pests. : [Corvallis, Or.] : Oregon State University Extension Service ; [Pullman, Wash.] : Washington State University Cooperative Extension ; [Moscow, Idaho] : University of Idaho Cooperative Extension Service ; [Washington, D.C.] : U.S. Dept. of Agriculture.