Santos, H. P. dos, Ambrosi, I., & Lhamby, J. C. B. (1999). Risk analysis of four crop rotation systems for wheat, over a ten-year period, in Passo Fundo, RS. Pesquisa Agropecuaria Brasileira, 34(4), 519–526. https://doi.org/10.1590/S1678-3921.pab1999.v34.5199