R. E. M. da Rocha, M. S. Pimentel, V. C. P. Zago, N. G. Rumjanek, and H. D. Polli, “Evaluation of biosolid fed by municipal waste-water sludge as a fertilizer in kale”, PAB, vol. 38, no. 12, pp. 1435–1441, Dec. 2003.