1. Atanassov, K.: Geometrical interpretation of the elements of the intuitionistic fuzzy objects, Preprint IM-MFAIS-1-89, Sofia, 1989. Reprinted: Int. J. Bioautomation, 2016, 20(S1), S27–S42 (1989)
2. Atanassov, K.: A second type of intuitionistic fuzzy sets. BUSEFAL 56, 66–70 (1993)
3. Atanassov, K.: Intuitionistic Fuzzy Sets. Springer, Heidelberg (1999)
4. Atanassov, K.: Remark on a property of the intuitionistic fuzzy interpretation triangle. Notes on Intuitionistic Fuzzy Sets 8(1), 34–36 (2002)
5. Atanassov, K., Szmidt, E., Kacprzyk, J.: On Intuitionistic Fuzzy Pairs. Notes on Intuitionistic Fuzzy Sets 19(3), 1–13 (2013)