Rossiello, Roberto Oscar Pereyra, et al. “Comparison of the Photoelectric and the Intersection Methods of Estimating Root Area, Root Lengh and Mean Root Radius”. Pesquisa Agropecuaria Brasileira, vol. 30, no. 5, May 1995, pp. 633-8, doi:10.1590/S1678-3921.pab1995.v30.4347.