Granato, T. ., Pietz, R. ., Knafl, G. ., CR, C. . , Jr, Tata, P. ., & Lue-Hing, C. . (1969). Trace element concentrations in soil, corn leaves, and grain after cessation of biosolids applications. Journal of Environmental Quality, 33(6), 2078-89. https://doi.org/10.2134/jeq2004.2078 (Original work published 1969)