Khan, Rashid Ali, and Nasru Minallah. “An Improved Blood Vessel Extraction Approach from Retinal Fundus Images Using Digital Image Processing: Blood Vessel Extraction Rom Retinal Fundus Images”. Proceedings of the Pakistan Academy of Sciences: A. Physical and Computational Sciences, vol. 54, no. 2, Apr. 2021, https://www.ppaspk.org/index.php/PPAS-A/article/view/242.