1. Ae N., J. Arihara & K. Okada, 1991. In: C. Johansen, K.K. Lee & K.L. Sahrawat (Eds.), Phosphorus nutrition of grain legumes in the semi-arid tropics, pp. 33–41. ICRISAT, Patancheru, Andhra Pradesh, India.
2. Agarwala S.C. & C.P. Sharma, 1979. Recognizing micronutrient disorders of crop plants on the basis of visible symptoms and plant analysis. Lucknow U.P./Department of Botany, Lucknow University, India.
3. Angélica Sadzwaka R., 1987. Agricultura Técnica (Chile) 47: 350–354.
4. Ayers A.D. & D.L. Eberhard, 1960. Agronomy Journal 52: 110–111.
5. Ayoub A., 1970/71. In: Annual report of the Hudeiba Research Station, pp. 60–80. Agricultural Research Corporation, Ministry of Agriculture, Democratic Republic of the Sudan.