1. Pawlak, Z.: Rough sets. Int. J. Comput. Inf. Sci. 11, 341–356 (1982)
2. Pawlak, Z.: Rough Sets: Theoretical Aspects of Reasoning About Data. Kluwer Academic, Dordrecht (1991)
3. Pawlak, Z., Skowron, A.: Rudiments of rough sets. Inf. Sci. 177(1), 3–27 (2007)
4. Pawlak, Z., Skowron, A.: Rough sets: some extensions. Inf. Sci. 177(1), 28–40 (2007)
5. Crespo, F., Peters, G., Weber, R.: Rough clustering approaches for dynamic environments. In: Peters, G., et al. (eds.) Rough Sets: Selected Methods and Applications in Management and Engineering. Springer, Berlin (2012)