1. Y. Imai and K. Iseki, On axiom systems of propositional calculi XIV, Proc. Japan Academy, vol. 42, pp. 19–22, 1966.
2. K. Iseki, An algebra related with a propositional calculus, Proc. Japan Academy, vol. 42, pp. 26–29, 1966.
3. Q. P. Hu and X. Li, On BCH-algebras, Math. Semin. Notes, Kobe Univ., vol. 11, pp. 313–320, 1983.
4. Q. P. Hu and X. Li, On proper BCH-algebras, Math. Japon., vol. 30, pp. 659–661, 1985.
5. D. Mundici, MV-algebras are categorically equivalent to bounded commutative BCK-algebras, Math. Japon., vol. 31, pp. 889–894, 1986.