Hodson, A.C., & Lofgren, J.A. 1960 Recognition and control of scale insects on trees and shrubs.. Extension Folder (Agricultural Extension Service, University of Minnesota) No. 207: [1-6 pp.].

Notes: Scales mentioned include oystershell scale, cottony maple scale, European fruit Lecanium, European elm scale, scurfy scale, pine needle scale, pine tortoise scale, and Fletcher scale.