， Standard Median: A. Bovik, Handbook of Image and Video Processing, Academic Press, 2000.
， Progressive switching median: Z. Wang and D. Zhang, "Progressive switching median filter for the removal of impulse noise from highly corrupted images," IEEE Transactions on Circuits and Systems II, 46 (1999), pp. 78-80.
， Multi-state median: T. Chen and H. R. Wu, "Space variant median filters for the restoration of impulse noise corrupted images," IEEE Transactions on Circuits and Systems II, 48 (2001), pp. 784-789.
， Directional difference-based switching median: Y. Hashimoto, Y. Kajikawa and Y. Nomura, "Directional difference-based switching median filters," Electronics and Communications in Japan, 85 (2002), pp. 22-32.
， Noise adaptive soft-switching median: H.-L. Eng and K.-K. Ma, "Noise adaptive soft-switching median filter," IEEE Transactions on Image Processing, 10 (2001), pp. 242-251.
， Improved switching median: S. Zhang and M. A. Karim, "A new impulse detector for switching median filters," IEEE Signal Processing Letters, 9 (2002), pp. 360-363.
， Adaptive median: H. Hwang and R. A. Haddad, "Adaptive median filters: new algorithms and results," IEEE Transactions on ImageProcessing, 4 (1995), pp. 499-502.
， Variational method: M. Nikolova, "A variational approach to remove outliers and impulse noise," Journal of Mathematical Imaging and Vision, 20 (2004), pp. 99-120.
， Our proposed algorithm: R. Chan, C.W. Ho, and M. Nikolova, "Salt-and-pepper noise removal by median-type noise detector and edge-preserving regularization." Accepted for publication by IEEE Transactions on Image Processing.