Thitiporn Chanwimaluang Guoliang Fan An efficient blood vessel detection algorithm for retinal images using local entropy thresholding. 21-24 2003 ISCAS (5) http://dx.doi.org/10.1109/ISCAS.2003.1206162 db/conf/iscas/iscas2003-5.html#ChanwimaluangF03