A. J. W. Rios, H. J. Kliemann, V. Álvaro de Oliveira, and P. K. T. Jacomine, “SAMPLING DENSITY AND LANDSCAPE COMPLEXITY IN SOIL SURVEYS CARRIED OUT IN BRAZIL”, Pesq. Agropec. Trop., vol. 38, no. 1, pp. 44–52, Mar. 2008.