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Ministerio de Acricultura y Ganaderia. 1982. Manual de 
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recomendaciones para cultivar cafe. 4ed. Oficina del Cafe, M.A.G. San Jose, 
Costa 
Rica. 52 p.
 
Pal, S. and M.B. Sengu~ta. 1985. Nature and properties of hurnic acid prepared from different sources and its effects on nutrient availability. Plant and Soil 
88(1) :71—91. 
Senn, T.L. 1987. Seaweed and plant growth. T.L. Senn. Clemson, South Carolina. 143 p. 
Tay, S.A.B., L.M.S. Palni and J.K. McLeod. 1987. Identification of cytokjnj.n gJ.uc~sjdesin.. a.~seaweed extract. ~.1.k’.Lant (rowt~ Regul. 
bt~):1i3—l~.
 
Vaugham, D. 1974. Possible mechanism for humic acid action on cell elongation in root segments of Pisum sativum under aseptic conditions. Soil Biology and Biochemistry
 
6(4) :241—247. 
Wellinan, F.L. 1961. Coffee: botany, cultivationand utilization. Leonard Hjil—Interscience, London. 488 p. 
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