5Barritt B H. 1998. Vertical aris training seen as alternative for apple. Good Fruit Grower, 39 (3) : 24 -26.
6Lakso A N, Roinson T L. 1989. The palmetto leader: A tree design for improved light distribution. HortScience, 24 (2) : 271 -275.
7Patricia S. 1990. Effects of orchard geometry on light distribution. Acta Horticulturae, 276:265 -272.
8Robinson T C, Seeley E J. 1983. Effect of light environment and spur age on Delicious apple fruit size and quality. J Amer Soc Hort Sci, 70 (6) : 855 -861.
9Robinson T L, Lakso A N. 1991. Modifying apple area canopies for improved production efficiency. HortScience, 26 (8) : 1005 - 1012.