R. P. Marques, D. Martins, S. Ítalo de A. Costa, and H. dos S. Vitorino, “Densities straw and luminosity conditions on seed germination on seed germination of Euhphorbia heterophylla”, Semina: Ciênc. Agrár., vol. 33, no. 3, pp. 867–872, Jun. 2012.