M. Sezgin and B. Sankur. Survey over image thresholding techniques and quantitative performance evaluation. Journal of Electronic Imaging. 2004, 13 (1): 146–165. doi:10.1117/1.1631315.
Nobuyuki Otsu. A threshold selection method from gray-level histograms. IEEE Trans. Sys., Man., Cyber. 1979, 9 (1): 62–66. doi:10.1109/TSMC.1979.4310076.
