Stephen Bassi Joseph, Emmanuel Gbenga Dada &. 2018. “Unsupervised Retinal Blood Vessel Segmentation Technique Using PdAPSO and Difference Image Methods for Detection of Diabetic Retinopathy”. Covenant Journal of Informatics and Communication Technology 6 (2). https://journals.covenantuniversity.edu.ng/index.php/cjict/article/view/1179.