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Tjhia, B.; Aziz, S. A.; Suketi, K. Correlations Between Leaf Nitrogen, Phosphorus and Potassium and Leaf Chlorophyll, Anthocyanins and Carotenoids Content at Vegetative and Generative Stage of Bitter Leaf (Vernonia Amygealina Del.). JTCS 2018, 5, 25-33.