C. C. Chang, Algebraic analysis of many valued logics, Trans. Amer. Math. Soc. 88 (1958), 467-490.
D. Dubois and H. Prade, Fuzzy Sets and Systems, Academic Press, Inc. [Harcourt Brace Jovanovich, Publishers], New York-London, 1980.
Sh. Ghorbani, On hyper MV-algebras, Ph. D. thesis, Shahbid Bahonar University of Kerman 2007.
Sh. Ghorbani, E. Eslami, and A. Hasankhani, Quotient hyper MV-algebras, Sci. Math. Jpn. 66 (2007), no. 3, 371-386.
Sh. Ghorbani, A. Hasankhani, and E. Eslami, Hyper MV-algebras, Set-Valued Math. Appl. 1 (2008), 205-222.
Y. B. Jun, M. S. Kang, and H. S. Kim, Hyper MV-deductive systems of hyper MV-algebras, Commun. Korean Math. Soc. (submitted).
Y. B. Jun, S. Y. Kim, and E. H. Roh, Bipolar fuzzy trabslations and extensions of ideals in BCK/BCI-algebras, Tamkang J. Math. (submitted).
Y. B. Jun and S. Z. Song, Subalgebras and closed ideals of BCH-algebras based on bipolar-valued fuzzy sets, Sci. Math. Jpn. 68 (2008), no. 2, 287-297.
K. J. Lee, Bipolar fuzzy subalgebras and bipolar fuzzy ideals of BCK/BCI-algebras, Bull. Malays. Math. Sci. Soc. (2) 32 (2009), no. 3, 361-373.
K. M. Lee, Bipolar-valued fuzzy sets and their operations, Proc. Int. Conf. on Intelligent Technologies, Bangkok, Thailand (2000), 307-312.
K. M. Lee, Comparison of interval-valued fuzzy sets, intuitionistic fuzzy sets, and bipolar-valued fuzzy sets, J. Fuzzy Logic Intelligent Systems 14 (2004), 125-129.
F. Marty, Sur une generalization de la notion de groupe, 8th Congress Math. Scandi-naves, Stockholm (1934), 45-49.
L. Torkzadeh and A. Ahadpanah, Hyper MV -ideals in hyper MV -algebras, MLQ Math. Log. Q. 56 (2010), no. 1, 51-62.
L. A. Zadeh, Fuzzy sets, Information and Control 8 (1965), 338-353.
H.-J. Zimmermann, Fuzzy Set Theory and Its Applications, Kluwer-Nijhoff Publishing, 1985.