title: Four low-cost monochromatic sources of known equal intensities.
authors.affiliation: Department of Plant Pathology, Bacteriology and Entomology, West Virginia University, Morgantown, West Virginia 26506.
authors.forename: K L
authors.initials: KL
authors.lastname: Poff
authors.forename: K H
authors.initials: KH
authors.lastname: Norris