“Mineral Nutrition of Cacao (Theobroma Cacao L. ) IV-Effects of Nitrate and Urea Nitrogen on Deficiency Symptoms of Phosphorus, Potassium, Calcium and Magnesium in Sand Culture”. 1965. Tropical Agriculture 42 (1). https://journals.sta.uwi.edu/ojs/index.php/ta/article/view/3793.