C. M. Cogo, J. L. Andriolo, D. A. Bisognin, R. dos S. Godoi, O. C. Bortolotto, and G. L. da Luz, “Nitrogen-potassium relationship for diagnosis of plant nutritional status and fertilization of the potato crop”, PAB, vol. 41, no. 12, pp. 1781–1786, Dec. 2006, doi: 10.1590/S1678-3921.pab2006.v41.7345.