6Bhaskar R. Bondada and James P. Syvertsen. 2003. Leaf chlorophyll, net gas exchange and chloroplast ultrastructure in citrus leaves of different nitrogen status. Tree Physiology, 23:553-559
7WilliamsRR. The effect of summer nitrogen applications on the quality of apple lossom . J.Hort.Sci.1965,40:31-41
8He, ZL; Calvert, DV; Alva, AK; Banks, DJ; Li, YC. 2003. Thresholds of leaf nitrogen for optimum fruit production and quality in grapefruit,Soil Science Society of America Journal, 67 (2) pp. 583-588
9Komamura, K; Suzuki, A; Fukumoto, M; Kato, K; Sato, Y Effects of long-term nitrogen application on tree growth, yield, and fruit qualities in a 'Jonathan' apple orchard Journal of the Japanese Society for Horticultural Science, 69 (5) pp. 617-623, 2000
10Neilsen D, Millard P, Neilsen GH, Hogue E.J. 1997. Sources of N used for leaf growth in a high density apple orchard irrigated with ammonium nitrate solution. Tree Physilogy 17:733-739
