Sulyok, Dénes, and Tamás Rátonyi. “The Role of the 4M-ECO Agrieconomical Modell in the Crop Cultivation”. Acta Agraria Debreceniensis0, no. 13 (May 4, 2004): 170-173. Accessed November 27, 2020. https://ojs.lib.unideb.hu/actaagrar/article/view/3406.