U. A. A. Vasconcelos, C. C. Costa, M. N. Oliveira, J. W. da S. Barbosa, A. B. de Medeiros, and T. Galvão Sobrinho, “Residual effect of sheep manure on lettuce cultivation at different spacings”, Green Journal, vol. 12, no. 3, pp. 508–511, Jul. 2017.