ZAMBILLO PALMA, M. A.; SILVA VOLPATO, C. E.; CASTRO DA SILVA, F.; DE SOUZA, P.; SILVA, J. A. Soil penetration resistence in coffe plantations cultivated with mechanized and manual systems. Coffee Science - ISSN 1984-3909, v. 8, n. 3, p. 364-370, 17 Jan. 2014.