1. Bodjanova, S.: Approximation of Fuzzy Concepts in Decision Making. Fuzzy Sets and Systems 85 (1997)
2. Chakrabarty, K., Biswas, R., Nanda, S.: Fuzziness in Rough Sets. Fuzzy Sets and Systems 110 (2000)
3. Dubois, D., Prade, H.: Putting Rough Sets and Fuzzy Sets Together. In: Słowiński, R. (ed.) Intelligent Decision Support. Handbook of Applications and Advances of the Rough Sets. Kluwer Academic Publishers, Boston (1992)
4. Greco, S., Matarazzo, B., Słowiński, R.: The use of rough sets and fuzzy sets in MCDM. In: Gal, T., Stewart, T., Hanne, T. (eds.) Advances in Multiple Criteria Decision Making. Kluwer Academic Publishers, Boston (1999)
5. Greco, S., Matarazzo, B., Słowiński, R.: Rough set processing of vague information using fuzzy similarity relations. In: Calude, C.S., Paun, G. (eds.) Finite Versus Infinite – Contributions to an Eternal Dilemma. Springer, Heidelberg (2000)