Núñez–Coba, N., and R. Escobar–Lorenzo. “The Current State of Learning of Agricultural Chemistry in the Formation of an Agronomist at the University of Holguin”. Revista Cubana De Química, vol. 29, no. 2, June 2017, pp. 255-6, https://cubanaquimica.uo.edu.cu/index.php/cq/article/view/2505.