A. Daza, C. Santamaría, M. Camacho, D. N. Rodríguez-Navarro, and F. Temprano, “Short communication. Influence of micronutrients on biological nitrogen fixation in bean (Phaseolus vulgaris L.) under greenhouse hydroponic culture conditions”, Span. j. agric. res., vol. 1, no. 3, pp. 77-80, Sep. 2003.