Gudzic, Nebojsa, Miroljub Aksić, Jasmina Knežević, and SlaviÅ¡a Gudžić. 2015. “Changes in Fertility of Vertisol and in the Content of Available Forms of Fe, Mn, Cu and Zn After Thirty Years of Using Phosphate Fertilizers”. Asian Journal of Agriculture and Food Sciences 3 (5). https://ajouronline.com/index.php/AJAFS/article/view/3069.